common greywater mistakes and preferred practices

8/7/2019 Common Greywater Mistakes and Preferred Practices

1/26


2/26

12/14/09 9:17 PMCommon Greywater Mistakes and Preferred Practices

Page 2 of 26http://www.oasisdesign.net/greywater/misinfo/index.htm#simple

w o e ng esection needs toload before it willjump).

Page numberreferences arefromThe NewCreate an Oasiswith Grey Water(book), fromwhich this list isexcerptedthenumbers don't goanywhere on theweb, but the hotlinks do.

Irrigation of vegetables with grey waterIrrigation of plants which can't take itPerforated pipe or other indeterminate system for grey water distribution

Garden hose direct from the back of the washerFreshwater designs & hardware used for grey waterBlackwater designs used for grey waterGrey water to drip irrigation

Automated reuse systems for flushing low usage (e.g., residential) toiletsReliance on government agencies or engineering firms for info on orconstruction of simple residential grey water systemsCA grey water law used as example to copy

Why Grey water Mistakes Don't Matter

Bad news: Greywater reuse offers much more benefits than are realized in mostsystems.

Good news: Even the worst shortfalls in greywater design rarely cause actualharm, and for the few that do, it's not much.

For every hundred greywater users in the US, probably 15 are achieving most ofthe benefit they should, eighty-some could do better, and a few systems haveoverall negative net benefit.

Of these, most have an overbuilt systemthe problem is that the ecological cost ofthe pumps and pipe are greater than the saved water.

Perhaps one greywater user in a thousand is discharging diaper greywater directlyto a water way, which is about the only way you can create a significant healthhazard. Almost all such systems date from a time when the ecosystem was muchbigger and the human imprint much smaller.

There has not been one documented case of greywater transmitted illnessin the US.

In our area, we have curbside recycling of mixed recyclables as well as trash pickup.

I've observed that well-meaning citizens put plenty of stuff which looks vaguelyrecyclable but is not in their recycling bins (e.g., polystyrene packing), as well astotally recyclable materials in in a form which is impractical to recycle, likethousands of bits of loose paper, broken glass, and specs of plastic. At the sortingfacility, they send this sort of stuff to the landfill.

For some households, the percentage of their recyclables which are actuallyrecycled is as low as 20%, though it could be 95% with good information. This
http://www.oasisdesign.net/greywater/misinfo/index.htm#lawhttp://www.oasisdesign.net/greywater/misinfo/index.htm#orghttp://www.oasisdesign.net/greywater/misinfo/index.htm#toilethttp://www.oasisdesign.net/greywater/misinfo/index.htm#driphttp://www.oasisdesign.net/greywater/misinfo/index.htm#blackwaterhttp://www.oasisdesign.net/greywater/misinfo/index.htm#freshwaterhttp://www.oasisdesign.net/greywater/misinfo/index.htm#washerhosehttp://www.oasisdesign.net/greywater/misinfo/index.htm#distributionhttp://www.oasisdesign.net/greywater/misinfo/index.htm#noh2ohttp://www.oasisdesign.net/greywater/misinfo/index.htm#veggieshttp://www.oasisdesign.net/greywater/createanoasis/index.htm


3/26



does not mean recycling is dangerous or illegal.

This is a totally different kind of "failure" than, say, burning PVC in the backyard(which forms clouds of carcinogenic dioxin). These folks just need to know whatthey're doing wrong, and how to do it better.

The aim of this web page is to share with greywater users and regulatorswhat they're doing wrong. The aim of our greywater books is to detail how

to do it better.

Please bear in mind as you read the exhaustive litany of "problems" that even themost pathetically misguided attempts at greywater reuse still wind up showingsome net benefit relative to the alternatives.

Here's an overview of the failure of greywater reuse to achieve more of the benefitwhich it easily could:

Most new complex grey water reuse systems are abandoned, most simpleones achieve less than 10% irrigation efficiency within five years.

If grey water treatment systems were built according to overdone legalrequirements, many would consume so much energy and materials to save solittle water that the Earth would be better off if the water were just wastedinstead.Claims made for packaged grey water filtration systems are often inflated.Some are very expensive and many don't work. Some also have thepreceding problem.The majority of successful grey water recycling systems are so simple andinexpensive they are beneath recognition by regulators, manufacturers,consultants, and salespeople.

A web search on "grey water" "greywater" "gray water" or "graywater" willyield hundreds examples of the errors below. Many are designs from the early70's, reprinted on the web as cutting edge, despite having been discredited inthe field for twenty years.

Pondering these failings has led our path further and further from the mainstreamof grey water thought.

If you're more realistic, you'll hit the target more often. Our designs are holding upwell in the field. In more than a dozen book revisions we've had to take back

almost nothing we've said.However, we haven't made as much of a difference as we'd like with our attemptsto popularize good design. The sorry state of average age grey water systems isnearly the same as when we started in 1989. The public remains vulnerable to thesiren song of grey water misinformation, the presentation of which is oftenauthoritative and polished.

So we now directly assault grey water misinformation as well, in a two-prongedeffort to get grey water systems to deliver more of their great promise.

This compilation is a free public service we are happy to provide. We love

feedback and new mistakes.

However, please don't request free private consultations on how to undo your
http://www.oasisdesign.net/faq/inquiry.htmhttp://www.oasisdesign.net/catalog/index.htm#set


4/26



mistakes or do it right in the first place. That's the paid work that supports thefree error warning service. Please buy a book, or commission an inexpensivereview of your project, or do the best you can the with info on this site, which isquite a lot. You'll find a bunch on this page, and more in the book excerpts, theconsulting examples, and on the eco design Q&A bulletin board .

Error-Assuming it's simple

Most of the errors below stem from this fundamental error, which in turn stemsfrom:

1) The instinctive recognition that in most cases the resource potential of the greywater (water, nutrients, embodied heat) is not worth very much in the scheme ofthings, and the costs of poor management (health threat, smells, etc.) are notvery high either, and

2) Failure to realize that a grey water system which achieves the common designgoals (e.g., saving water and resources, and/or achieving disposal in a sanitary,low maintenance way) is a more site and user specific design problem than almostany other home-scale appropriate technologymore than solar heat, compostingtoilets, rainwater harvesting, ecological building materials, etc...

In other words, grey water seems like it should be simple, and people don'tallocate grey water system design the effort required to achieve the performancethey expect.

Preferred practice

Either lower your goals or put more thought/ energy/ money into the design.Reading this page, the grey water Q& A page, and our grey water books is a goodstart. If your site is difficult, your goals high, or your time short, consider a designconsultation as well.

Exceptions

If the performance goals are low enough for the context, grey water systems ARE

simple. The "drain out back" is a very common example of a "system" whichdoesn't ask for or give much.

^List of errors ^ Grey water central

Error-Out of context design

Wetlands in the desert. Irrigation of a swamp. Sand filtration, ozonation,

and reuse for flushing toilets in a residence. Each of these are valid designsbut applied in the wrong context. In a culture where standardized solutions arethe norm from coast to coast, it is hard to remember the necessity of paying
http://www.oasisdesign.net/greywater/index.htmhttp://www.oasisdesign.net/greywater/misinfo/index.htm#contentshttp://www.oasisdesign.net/design/consult/index.htmhttp://www.oasisdesign.net/catalog/index.htm#sethttp://www.oasisdesign.net/faq/index.htmhttp://www.oasisdesign.net/faq/index.htm#greywaterhttp://www.oasisdesign.net/design/examples/index.htmhttp://www.oasisdesign.net/catalog/index.htmhttp://www.oasisdesign.net/greywater/index.htmhttp://www.oasisdesign.net/design/consult/index.htmhttp://www.oasisdesign.net/catalog/index.htm


5/26



primary attention to the context, let alone know how to do it.

Almost every time I say that something is so, the next breath is spent explainingwhy it is not so in slightly different conditions. People often seize on a principleI've mentioned in one context, then vigorously misapply it to the next. As soon asI've explained the principle which overrides it in case two, they apply THAT to casethreethis can go on for hours.

Preferred practice

The most general principle of grey water system design is that there are nogeneral principles. All appropriate technologies are context specific (that is part ofwhat makes them appropriate) however grey water reuse is EXTREMELY contextspecific. The final section on each of the common mistakes describes the inevitableexceptions when it isn't a mistake. Reuse or treatment, new construction orretrofit, soil and climate conditions, legal considerations; each of these variables inparticular have the potential to change the design completely. Carefully check the

list of grey water system design variables (page 8) and what to do about them inthe balance of the grey water books. General background on context specificdesign can be found inLiving with Nature (book)(see inside back cover) from whichthis summary is excerpted:

Context specific design: While there are no solutions which apply universally,there are a variety of approaches and patterns which can be applied to generatethe optimum solution for any need in any context.This is a vitally important principle of ecological design. In all cases the greatestefficiencyand quality as wellis achieved when the power of the tool is well

matched to the task at hand. Frequent technological overkill is one of the saddestsources of waste in our society. Elimination of overkill does not involve realsacrifice. The resources saved by using simple tools for easy tasks can be appliedtowards performing more difficult tasks. Using transportation as an example,walking would be used for the tasks for which it is adequate, bicycles for distancestoo long to walk, busses and trains for distances too long to bike or in badweather, planes for speed or great distances, and cars for special applications likeambulances, mobile homes, or workshops. Getting superfluous cars off the roadwould enable the necessary ones to get around without being choked by traffic.

Cleverly matching the power of the tool to the task at hand is cheaper, healthier,has lower environmental impact and is more enjoyablebut ultimately morepowerful than any single solution. Though uniform solutions appeal to centralizedbureaucracies, attempting to implement a single solution across the board, withoutregard to context, will generate a host of new problems. Bare sufficiency producesoptimal growth; deficiency is stunting, excess imbalancing.

Those readers who are used to single solutions will be quick to point out situationswhere, for example, a composting toilet is unsuitable. None of the solutionsproposed here are applicable across the board, nor is it suggested that any of thetechnologies criticized here should be eliminated completely. What is suggested is

that a range of solutions be matched to the range of contexts using commonsense.
http://www.oasisdesign.net/design/book/index.htm


6/26



This system spotted at the Los Angeles Eco

Expo demonstrates a number of mistakes.

First, there's overkill. For several thousand

dollars it does what a $400 "drum with

pump" does. Second, the pictures on the

poster board show filtered but unsterilized

grey water coming out at high pressure

through sprinklers and inundating a

concrete walkway from both sides. That

violates three health principles (at least it

didn't show kids dashing through the

sprinklers). The tank is also too big, so thatviolates a fourthprobably a record for

Exceptions

There are no exceptions to the "no general principles" rule.


Error-Overly complex, delicate and/or expensive systems with

negative net benefit

As a class, these systems fail to refer to the big picture. A typical residential greywater system will save $5-$20 worth of freshwater a month, at best. This meansthat if the system costs several thousand dollars, the owner would have beenbetter off just paying for the extra water, and the Earth would have been less

impacted by the wasted water than the wasted pumps, valves, piping, filters, andelectricity used by the overbuilt system. It is this constraint more than any otherwhich makes good grey water system design a real challenge. Complying with the"actual net benefit" requirement is so difficult in practice that it is very commonfor systems to just be built anyway, often with vague allusions to "demonstrationproject"I feel this justification should be used sparingly, otherwise we will end upwith lots of demonstrations of how yet more resources can be wasted.

In a residential context, any system which uses apump, filter or costs more than you spend on waterin a year is suspect. Disinfection is extremelysuspect. Systems which entail massive, permanentdisturbance to the planted area, such as the state ofCalifornia's mini-leachfield system, which involvesburying truckloads of gravel in your garden, are alsomissing the point.

Unfortunately, strict interpretation of therequirements of grey water laws which are stillworks in progress tends to drastically reduce or

completely destroy any possible economic benefits,in some cases without any benefit (except thatreducing the proliferation of grey water systems wasa perceived benefit to some of the major architectsof the laws. See "Needed improvements toCalifornia's grey water law," in the Builder's GreyWater Guide).

Preferred practice

Choose the SIMPLEST possible design, and BUILD ITAS WELL as you possibly can. Keep one eye on your
http://www.oasisdesign.net/greywater/law/improve/cpcupc.htmhttp://www.oasisdesign.net/greywater/index.htmhttp://www.oasisdesign.net/greywater/misinfo/index.htm#contents


7/26



one system.original goals and the big picture throughout theprocess (see page 8). Keep asking yourself what thesystem is likely to look like in flood, drought, or in twenty years after threeowners. What is most likely to have failed or been abandoned? How is the systemlikely to have been patched? Often the way systems get patched or modified laterto comply with reality is the way they should be designed to be used in the firstplace. If no patch seems acceptable, there is a good chance the system should notbe built that way at all.

Exceptions

When and wherever grey water is more valuable, the ground rules shift. Greywater skyrockets in value during drought emergency, and anywhere that otherwater sources are not available.

If grey water is the only way to save a $20,000 landscape during a drought, an

expensive system that falls apart in a year may be justifiable. On the other hand,a very well-built, simple system which lasts for decades could possibly be madefor the same price, if the design resources are available.

I designed a series of simple, very well-made grey water systems for a housewhere the only water supply is rainwater, stored for the eight month dry season ingiant cisterns. The grey water system cost a few thousand dollars, but can providethe same amount of water as a cistern which would cost about ten thousanddollars. It also uses a fraction of the material and also solves the problem ofdisposing of the grey water.

Acute disposal problems can change the picture. I got a call from one Alaskan oilcamp where the grey water from several hundred people was boiled down to ash,and the drums of ash shipped to the continental US for disposal (don't you love oilcompany engineers?) Compared to this, almost any system would be cheaper,simpler and more ecological.

A hotel in Big Sur was sending out their laundry at a cost of a few thousanddollars a month because they could not make a conventional on-site disposalsystem which could handle the water. A large, complicated, but well-built grey

water system enabled them to do the laundry themselves, and they were able topay off the investment in less than a year.

Sheer volume shifts the economics drastically. Almost any institution with severalthousand gallons a day of grey water production and a like amount of irrigationdemand would find that a complex system capable of treating the water so it couldbe distributed efficiently through irrigation hardware could be paid off in a fewmonths to a few years.

US regulators are more comfortable with complex, expensive engineered systems

than mysterious biological systems. It may be the case that an overly complexgrey water system is the best alternative to an even more overbuilt conventional


8/26



system, if that's all they'll let you do.


Error-Mansion with a grey water systemThis is a specific case of the general problem described above. A grey watersystem for a 2500-5000 square foot house with a half to five acres of irrigatedarea and four or six inhabitants is virtually assured to be a grey water system withnegative net benefit. In this situation, the resource value of the grey water isliterally a drop in the bucket compared to all the other waste going on, andattempting to capture it just adds more waste. A one-bathroom house mightrequire thirty feet of extra pipe to be dual plumbed, a mansion could easily requirehundreds of extra feet of pipe for dual plumbing. When you add the level of

construction perfection and use convenience required to fit in with the rest of thehouse, the resource cost of the system compared to its use value can becomeludicrously out of balance.

Preferred practice

Build a smaller house. A house half as big built with completely conventionalbuilding materials and systems is almost certainly more ecological than a "green"mansion. In the US in the fifties the average house was nearly half as big as now.Focus all that money and energy on making a good, space efficient design, and

you'll have lots left over to do state of the art green materials and systems (SeeLiving with Nature (book))

If you must have a huge house, don't try to dual plumb it. Go after the combinedgrey water and blackwater, treat it with (for example) a septic tank and sandfilter, and distribute it through efficient drip irrigation. You drastically reduce theplumbing cost, you get significantly more water and nutrient volume, and the dripirrigation can reuse it with many times more efficiency.

Exceptions

The argument is frequently advanced that huge "green" custom homes nourishproviders of green technologies with a huge infusion of money. As one of theaffected professionals, I am not immune to this line of logic. My personal standardfor taking on a job of this sort is that if the owner is willing to commit themselvesand other users to significant lifestyle accommodation for the earth, and take therisk of pioneering new designs, then I'll do it. Redefining the comfort andconvenience standard (lifestyle accommodation) can easily cut the environmentalimpact of the project in half, and furthermore, promotes the idea of earthawareness and accommodation to an influential class of people. The benefits of

supporting pioneering are obvious. Still, these goals can be accomplished evenbetter in fewer square feet. One of the most powerful lifestyle statements I've
http://www.oasisdesign.net/design/book/index.htmhttp://www.oasisdesign.net/greywater/index.htmhttp://www.oasisdesign.net/greywater/misinfo/index.htm#contents


9/26



personally witnessed is a very successful attorney and his wife living happily forseveral years in a tasteful 120 square foot cottage on a multi-million dollar lot inSanta Barbara (that's the size of the master bedroom closet of the house you'dexpect these people to own!)

For a letter on this topic, click here.


Error: Pump enthusiasm

For some reason many people reflexively reach for a pump when they want tomove grey water around. There is no denying that it is very cool the first day tosee grey water squirting out where you want it thanks to a pump. What you don't

realize is that the pump is the first step on a slippery slope- this error is the mostcommon subset of the one above. It won't work very long without filtration, andfiltration is a big hassle (see Error: Grey water to drip irrigation for a typicalfiltration story). Grey water handling is a long term issueyour house is still goingto be generating grey water in thirty years, but pumps are not a long termsolution. Odds are about 10 to 1 that your grey water system isn't going to be stillbe in use in even five years if it uses a pump. If the pump hasn't been killed bytwo foot long hairs which worked their way through the 75 micron filter andwrapped around the rotor, or by you when the float switch hung up at three in themorning and stayed on noisily for the third night in a row, that's about the time it

will die of old age. Unless you're really fanatically enthusiastic about cleaning fetidfilters after doing it 100 times in five years (often during parties when the usepeaks ) you probably won't buy a replacement.

Even if everything works perfectly, the pump sucks a lot of electricity; it willtypically be the number 2 to 5 energy using appliance in the home, so for all youreffort you've just substituted electricity waste for water waste.

Preferred practice

Use one of the systems which doesn't need a pump. There is information aboutpumps and filtration options in the appendices ofCreate an Oasis with Grey Water.

Exceptions

If 100% of your potential irrigation area is higher elevation than your grey watersources, you'll have to either forget about reusing your grey water or get a pump.For institutional contexts where there is more than 300 gallons a day of greywater generation and a like amount of irrigation need, the water can easily beworth more than the fancy filtration and pumping hardware needed to manage the

large volume, even if it all has to be replaced every five years. At present themarket is very weakly developed for volume grey water reuse hardware andsupport, but at least theoretically it is a legitimate application for a pump.
http://www.oasisdesign.net/greywater/misinfo/index.htm#driphttp://www.oasisdesign.net/greywater/index.htmhttp://www.oasisdesign.net/greywater/misinfo/index.htm#contentshttp://www.oasisdesign.net/faq/green4000ft2home.htm


10/26



Beautifully made but ill-conceived grey water storage tank. This four

foot wide, four foot deep tank is the final of a four-chamber system

which converts grey water to foul-smelling blackwater over the course

of the week it takes to get through the system. The water is dark black,

smells wicked, and generates hydrogen sulfide which has eaten

through the steel lid.


Error: Storage of grey water

Storage rapidly turns grey water into blackwater (see photo, page 4). The word"storage" should immediately sound an alarm, as should anything that includes atank bigger than 55 gallons (for residential systems). If you doubt this, just fill abucket with grey water and observe it as it progressively darkens and becomesmore fetid. Bacteria multiply to blackwater levels as well, at least the indicatorbacteria. In Mexico the trampa de grasa (grease trap) often included in grey watersystems is a very popular way to commit this mistake-omitting or bypassing thetrampa de grasa would be much better.

Preferred practice

24 hours is generally consideredthe prudent maximum time forstorage. Since this is not enoughtime to, for example, store greywater from a time when irrigationis not needed to one in which it is,I find myself tuning designs toeliminate pooled grey wateranywhere it occurs; just send it allstraight to the soil. The fewer littleanaerobic corners and pockets thebetter. My latest designs drainCOMPLETELYall the collectionplumbing, distribution plumbing,and surge tanks (if any) slope atleast 2% across their bottomsurfaces.

Manually distributed grey watercan be stored for the day to allowfor manual distribution all in onesession. Tanks for this purposeshould be designed to drain COMPLETELY (not leave a bit of fetid grey water at thebottom to inoculate the next batch) and NOT BE TOO BIG as this invites misuse inthe form of letting the water sit too long.

Exceptions

Highly treated grey water (for example, after a septic tank and constructedwetland) can supposedly be stored for up to a month before it goes septic,
http://www.oasisdesign.net/greywater/index.htmhttp://www.oasisdesign.net/greywater/misinfo/index.htm#contents


11/26



depending on the BOD and temperature.

Surge tanks, which absorb peak flows (say from a bathtub and washing machinedischarging simultaneously) then let them out immediately at a reasonable rateare OK.

Really cold grey water takes longer than 24 hours to stink, though I'd have tohave a really persuasive reason to want to rely on this for the design of a system.

Grey water can be filtered effectively by settling in a septic tank, but then itwill stink to high heaven and must be handled like clarified blackwater from aseptic tank. In this case, the longer it sits in the septic tank the better (lowersuspended solids and BOD).


Error: Cavalier disregard for legitimate public health concerns,and/or excessive paranoia about negligible health concerns

Some voices on the Web advocate growing lettuce and carrots with untreated greywater. Others fret about distributing grey water under nine inches of soil withoutdisinfection. Some people worry about eating fruit which contains molecules frombiodegraded dish soap, forgetting that they imbibe larger traces of dish soapdirectly with every glass of water and plate of food.

Preferred practice

Each user has to find their own comfort point on the paranoia vs recklessnesscontinuum, and each community has to determine the outer limits of recklessnessit will tolerate. Grey water reuse poses a very mild health threat in overdevelopedcountries. Despite all sorts of grievous misuse (brought on in part by lack of usefulregulatory guidance), there has not been a single documented case of grey watertransmitted illness in the US. At the same time, it's definitely poor form toconstruct pathways for infecting people into your design, and totally unnecessary.Proper handling (using the same principles on page 4) can eliminate the healththreat from grey water in third world countries.

Here's an overview of health concerns and what to do about them, from Create anOasis with Grey Water:

Health Considerations Concerning Grey water Use

All grey water safety guidelines stemfrom these two principles:

1) Grey water must pass slowly throughhealthy topsoil for
http://www.oasisdesign.net/greywater/createanoasis/index.htmhttp://www.oasisdesign.net/greywater/index.htmhttp://www.oasisdesign.net/greywater/misinfo/index.htm#contents


12/26



Grey water "main" running down a Tijuana street a bona

fide health threat. In theory, this water could produce fruit and

green relief in a sanitary way. Unfortunately, extremely high

salt concentration from hand washing with small amounts of

hand-carried water and generous amounts of "Fab one-Shot"

from little day-glo packets renders this resource unusable; even

though it is year-round water in a desert, not even weeds grow

from it. A enlightened soap factory with a line of biocompatible

cleaners and a suitable marketing plan could dramatically

transform the colonia environment, exchanging fetid, mucky

streets for thriving, shade, and fruit-providing large trees.

natural purification to occur.2) Design your grey water system so nocontact takes placebefore purification.

Here are examples of applying theseprinciples to correct possible problems:

Direct contact or consumption.Solution: carefully avoid crossconnections and label grey waterplumbing, including grey watergarden hoses. Use gloves whencleaning grey water filters.Breathing of microorganisms.Droplets from sprinklers can

evaporate to leave harmfulmicroorganisms suspended in theair, waiting for someone to breathe them. Solution: don't recycle grey waterthrough sprinkler.Microorganisms on plants. Direct application to foliage can leave untreatedmicroorganisms on surfaces. Solution: don't apply grey water to lawns (see ANote on Lawns, page 8) or fruits and vegetables that are eaten raw(strawberries, lettuce, or carrots, for example). Fruit trees are acceptable ifgrey water is applied only to the roots.Contamination of surface water. If grey water does not percolate through

the soil, it can flow into creeks or other waterways untreated. Solution:discharge grey water underground or into a mulch-filled basin. Don't applygrey water to saturated soils. Apply grey water intermittently so that it soaksin and soil can aerate between waterings. In general, contained grey waterapplication at least 50 feet from a creek or lake is not a problem.Contamination of groundwater. It is all but impossible to contaminategroundwater with a grey water system. However, property owners with wellsshould not irrigate with grey water any closer to the well than countyregulations allow for a septic tank leachfield.Chemical contamination. Biological purification does not usually remove

industrial toxins. Toxins either will be absorbed by plants or will pollutegroundwater. Many household cleaners are composed of chemicals that areunsuitable for introduction into a biological system. Solution: don't buyproducts that you wouldn't want in your grey water system. Divert watercontaining those you can't avoid to poison the sewer or septic instead.System overload. Grey water systems are safest when using water that isfairly clean initially. Grey water should not contain water used to laundersoiled diapers or by anyone with an infectious disease; in both cases, greywater should be diverted to the septic tank or sewer. Also, don't store greywater; use it immediately, before bacteria multiply. Finally, if you are having

a party where 50 people are going to use a system designed for two,consider diverting grey water to the sewer for the night.


13/26




Error: Treatment before irrigation

Plants and soil, especially the upper, most biologically active layer of soil, arefantastically effective for wastewater treatment. Pretreatment is often presented asan essential element in a grey water system, when in fact it may be morepointless than treating your wastewater before sending it down the sewer. Plantsand soil are fine with funky, chunky water; it is pipes and people who may have ahard time with it. Pretreatment is only necessary to overcome limitations of thedistribution plumbing to handle funky water. With a properly designed system,even straight kitchen sink water (very high suspended solids) can be reliably andsafely distributed with no filtration whatsoever (photo, page 30).

Preferred practice

For simple residential systems, the preferred alternative to pretreatment is to 1)design the distribution system so it can handle funky water, in particular, highlevels of suspended solids, and 2) design the distribution system so human (oranimal) contact is unlikely to occur before the water has passed slowly throughhealthy topsoil (i.e., before it's purified)."The Branched Drain to Mini-Leachfields" system I developed is an example of asystem that fulfills these requirements in their most fanatically stringentinterpretation; the smallest orifice in the system is an inch and a half, and there

are no filters, pumps, valves or surge tanks to foul with solids. Distribution can befully subsurface (see page 13 and pages 11-14 in the Builder's Grey Water Guide).These requirements can be fulfilled adequately by several other systems wheregrey water daylights for two inches before disappearing into mulch filled basins.

Exceptions

The systems described above are restricted to the use of large diameter, drain-type distribution plumbing, which is inherently less efficient than, say, dripirrigation plumbing. For small-scale systems, it is generally best to eat thisefficiency loss, or go to a more labor-intensive, less sanitary system likebucketing.For larger flows, say several hundred gallons a day or more, and a like amount ofirrigation need, it can be very economical to pre-treat grey water to the point thatit can be distributed by more or less standard irrigation hardware.


Error: Discharge of greywater directly into natural
http://www.oasisdesign.net/greywater/index.htmhttp://www.oasisdesign.net/greywater/misinfo/index.htm#contentshttp://www.oasisdesign.net/greywater/buildersguide/index.htm#brancheddrainhttp://www.oasisdesign.net/greywater/index.htmhttp://www.oasisdesign.net/greywater/misinfo/index.htm#contents


14/26



Soapy creek from a legacy system at

a hot springs resort constructed in

pristine wilderness around the turn

of the century.

A laundry pipe runs out the formal

drive of an estate in the foothills

above Los Angeles, and discharges

into the gutter, in which it runs for

a hundred yards before running

into a gulch.

waters or hardscapes

You'd think this would be morerare, because it is so obviouslywrong. They come in twocategories; legacy systems, from

places built 50 or 100 years agobefore they knew any betterand/or before it mattered, andnew systems, which are generallymore furtive and criminal-feeling,or just so unconscious it is beyondbelief (photo below, page. 4).

Preferred practice

Almost anything would be preferred. Just dumping the water on the surface of thesoil is a big improvement over dumping it in natural waters or impermeablesurfaces. Dumping it into a mulch-filled basin would be a vast improvement.

Exceptions

When the receiving body of water has sufficient capacity to purify the water, andthere is no other reasonable alternative. Sailboats on the open ocean are the onlyexample which comes to mind. Even if you are in the middle of a vast wilderness

next to a large river, you can just take a few steps back and rinse the shampooonto soil, which will purify it before it goes into the river.


Error: Use of grey water for irrigating lawns

The only proven safe and reliable way of irrigating lawns with grey water is

through underground drip tubing supplied by a backwashing sand filter typesystem; far beyond what most residences are likely to install. Unfortunately, turfaccounts for the bulk of the irrigation need in the typical landscape, and lawn greywatering is by far the most prevalent violation of common sense grey water safetyrules.

This is awkward to write. Do I criminalize thousands of grey water users who seeno harm in what they are doing, or do I condone a marginal activity?

If the lawn receives traffic, by applying grey water to the surface you are shortcircuiting the all-important purification step (see health rules pages 4, 8), inviting

direct contact with untreated grey water and the possibility of transmittingpathogens. The likelihood of transmitting disease is small (it would be laughed off
http://www.oasisdesign.net/greywater/misinfo/index.htm#healthhttp://www.oasisdesign.net/greywater/index.htmhttp://www.oasisdesign.net/greywater/misinfo/index.htm#contents


15/26



in most developing countries) but it exists. The nightmare scenario: the day carecenter that "saves money and the environment" by irrigating the lawn with diaperwash water, which a dozen toddlers from other families then play in (I know youthink I'm making this up, but I saw it at my daughter's very highly regarded daycare; they were just trying to do the right thing and spaced out a bit about thecontext).

If the lawn doesn't receive traffic, then it is less risky to irrigate it with grey waterbut it shouldn't be a lawn in the first place; the only legitimate reason to have oneof these resource hogs is that they are more fun to play on than, say, a graveland cactus garden. A better solution would be to replace the un-trafficked lawnwith something else and irrigate that with grey water, if it needs irrigation at all.

Besides the health issue, grey watering a lawn is a pain in the rear. The systemalmost universally used is a hose from the washing machine or house plumbingwhich is moved around. Since the water has to be applied within the root systemto benefit the plant, you have to move this hose to numerous locations in a verysmall grid, as compared to say, a large fruit tree, which would benefit from waterleft to dump anywhere within an area of hundreds of square feet.

Perforated pipe under the lawn will have efficiency in the single digits, and leavesome areas completely dry.

Preferred practice

We suggest that you replace most of your turf with something else, replace what'sleft with a water-conserving grass such as Tall Fescue, watered with the freshwateryou save from using grey water elsewhere, or just let your lawn go dormant when

there's not enough rain to sustain it.

Exceptions

Lawns can be irrigated well and safely through subsurface drip ($1500 on up. 300gpd grey water generation/irrigation need is the break even point where such asystem starts to make sense).


Error: Use of grey water for irrigating vegetables

The primary reason not to use grey water on veggies is concern about transmittingdisease (see page 4). Some people use grey water on veggies anyway. Why? Seeexceptions, below.

Preferred practice
http://www.oasisdesign.net/greywater/misinfo/index.htm#healthhttp://www.oasisdesign.net/greywater/index.htmhttp://www.oasisdesign.net/greywater/misinfo/index.htm#contents


16/26



A probable exception: veggies irrigated subsurface

with grey water in a greenhouse (the plumbing is

shown in a photo on page 22).

If your goal is to just get rid of grey water responsibly and irrigation is not neededthere is no reason to put it on food crops. If your goal is water reuse to loweroverall water consumption, chances are that you will have more irrigation demandthan you have grey water supply. In this case, use grey water first onornamentals, then on fruit trees, and then use the fresh water you saved onveggies.

Exceptions

In the past I have categorically recommendedagainst using grey water for irrigating vegetablegardens. As a certain fraction of grey waterusers have always and will always do it anyway,I've decided to illuminate the boundary betweenresponsible resource reuse and reckless publichealth threat in this area. Also, after irrigating

veggies with grey water myself, I understand theattraction better. We have a vast drip irrigationsystem, but it does not adapt well to irrigatingveggies. The hardware is not that great;sprayers have very uneven coverage, they putthe water on top of mulch instead of under, andyou have to build the bed to match the spray pattern, except that wind blows thispattern completely off course. Lines with emitters in line are super expensive, andhave clogged rapidly from filtered potable water. Additionally, I can't just hook upto one of the other irrigation zones; the veggies need about ten minutes every

day, instead of, say an hour and a half three times a week. Also, during weeding,seeding, transplanting, growth and harvest the irrigation need variestremendously. Veggies also are much more sensitive to daily (even hourly)changes in weather than fruit trees. They are a very poor fit to an automatedsystem; I would probably have to settle for less than 30% irrigation efficiency,whereas I'm used to 80% for my fruit trees. Even if I wanted to pay for it, oursmall community water system doesn't really have this water to spare during thehot, dry summer months. Handwatering is the obvious alternative, and if I'mhandwatering anyway, why not use hoses or buckets of free grey water, instead offresh water which costs me nearly a penny a gallon? When hand watering with

grey water I can get 80% irrigation efficiency, and am much more tuned into theplants.

With the grey water systems I recommend there are several layers of protection,each capable of preventing the spread of infectious microorganisms on its own.When irrigating veggies with grey water the only possible protection is from 1) nothappening to have anything nasty in the water, 2) not splashing grey water on theedible portions, 3) washing veggies, 4) cooking and 5), not getting sick even ifyou eat something nasty. Each of these offers tenuous protection. Additionally,grey watering vegetables is often manual, which inevitably results in some direct

contact with grey water. If you're going to engage in this reckless practice, payattention to what's happening with this slim margin of safety. If anyone in your


17/26



This is the most dramatic case I've ever seen of

this problem. These two giant coast live oak

trees toppled, with dry season grey water

application as the suspected culprit (dry season

irrigation promotes root disease in these trees).

Mysteriously, oaks with grey water applied to

them across the street don't seem any worse for

the wear.

household has an infectious disease, protection 1) is not operative and you shouldstop using grey water on veggies. For 2), exercise care in applying grey water,and give crops which are splashable and eaten raw a wide berth, even more so asharvest time approaches (e.g., carrots, salad greens). Always wash grey wateredraw veggies with soap, iodine, or equivalent. Try not to splash too much, andwash your hands after grey watering (this extra wash water has to be consideredin the irrigation efficiency for this system). As a last resort, hope for not gettingsick even if you eat something nasty. I'm reluctant to mention this factor, but itseems to work in much of the Third World, where people catch plenty of nastydiseases but still not as much as you'd think.


Error: Irrigation of plants which can't

take it

Certain plants cannot take grey water, and certainplants can't take too much of any kind of water.Acid-loving plants tend to have a hard time withgrey water, and certain plants which are native todry areas have a hard time handling any irrigationin the dry season. Also, some cultivated plantshave problems with soggy conditions.

This problem is not a commonly encountered one.

Preferred practice

Avoid irrigating plants which don't want thewater, and design your system so it doesn'tcreate soggy conditions for plants that can'thandle it.


Error: Distribution of grey water through perforated pipe or

other system where you can't tell where the water is going

There are two problems with distribution of grey water through perforated pipe:

One, it will clog
http://www.oasisdesign.net/greywater/index.htmhttp://www.oasisdesign.net/greywater/misinfo/index.htm#contentshttp://www.oasisdesign.net/greywater/index.htmhttp://www.oasisdesign.net/greywater/misinfo/index.htm#contents


18/26



Why doesn't perforated pipe clog in septic tank leachfields? Because a septic tankis highly effective for removing suspended solids. Suspended solids are plentiful ingrey water, even after the crude types of filtration sometimes attempted in home-brew systems, and these will eventually clog the pipe. If that doesn't clog it first,root infiltration will. If the pipe is big enough, and the grey water clean enough, itmay take so long to clog that the durability is acceptable, but this is rare. A rarely

used bathroom sink going into ten feet of four-inch pipe in gravely soil might lastseveral years before failing. Laundry water will quickly clog almost any sizedsystem.

Two, it is terribly unmanageable for irrigation

Any system where you don't know where the water is going is all butunmanageable for irrigation. This is only a problem if you are trying to reuse thewater, not if you are just trying to get rid of it. The problem with any system

where there are emitters lined up in series (like holes in perforated pipe) is thatthe majority of the water will dump out the first few holes, or the lowest fewholes, depending if the flow is low or high. Then these holes will clog, and thewater will all go out the holes next door. In order to actualize irrigation watersavings, you have to somehow coordinate with fresh water irrigation so that allthe plants are getting watered enough but not too much. This is all but impossibleto do with perforated pipe, which will invariably water one small area way toomuch the rest hardly at all, in a pattern which is constantly changing and invisible(if the pipe is buried) except in the form of distressed plants.

You may be able to tune the pipe slope, hole spacing and size such that each holespits out the same amount of water along the entire length of the system. Thisexercise has been performed by numerous grey water experimenters before you.However, this perfection is very fragile. If you alter the slope 1%, the flow a fewpercent, or if lint comes down and blocks some holes, the distribution evennesswill all go to hell!

A series of garden beds with water flowing in gravel underneath is anotherexample. Will the first bed get 90% of the water because the plants suck it upbefore it can move on, or the last bed, because it is low and the water rushes

down to it? Who knows?

Three, gravel is nasty in the garden

Most perforated pipe systems have gravel around them. Most greywater users arekeen gardeners. Gravel is the last thing you want in your garden; it degrades soiland makes digging really difficult. If you wrap the gravel with filter fabric tocontain it, that will clog, as well as turn to lots of bits of plastic trash over time.

Preferred practice

Use gravelless infiltration galleys or subsurface drip for subsoil distribution. If you


19/26



must have perforated pipe, add it as an extension to your septic tank leachfieldand filter the grey water through the septic system so the pipe doesn't clog. Thepreferred practice for separate disposal of residential grey water are mulch filledbasins supplied by drain out back, or a branched drain network, with pipes a fewinches above the mulch if allowed or in good sized underground chambers ifsubsurface discharge is required (page 13, pages 11-14 Builder's Grey Water

Guide (book)).The preferred practice for reuse is to plumb in such a way that you

know with some certainty where the water is going, so you can adjust yoursupplemental irrigation accordingly. This typically means a parallel system, or onewith only one outlet. Examples are drain out back, movable drain out back,branched drain networks,Laundry to Landscape, well-made and regularly serviceddistribution boxes, bucketing, etc. Crude but effective parallel splitting of greywater flows can be achieved by not combining the flows in the first place; eachfixture has its own separate outlet. This is difficult to manage if the fixture use ishighly variable and/or unknown, but works adequately in some applications.

For reuse of large flows, high level treatment and underground drip irrigation ispreferred (pages 24, 8).

Exceptions

Effluent with suspended solids removed, for example, by a septic tank or sand-filtration, can be discharged through perforated pipe. For even irrigation, 1"pressurized perforated pipe lines with 1/16" holes on 1" centers up to 50' longhave been used (photo, page 22).

I've heard reliable accounts of a few gravel pit or trench systems which have beenworking for ten years or more with shower water only. Perhaps there is somethingmagic about these installations, or shower grey water in general?

Laundry water is normally the worst, however...I have seen an old fashioned claydrain tile line which handled laundry grey water for thirty years in fairly heavy soilwithout clogging. Even though it was not failing, it was replaced with a modernperforated pipe as part of a remodel. The modern replacement clogged completelyin less than a year and was abandoned.


Error-Garden hose direct from the back of the washer

This method works until or unless any of these problems occur: 1) the hose kinksand the washing machine pump burns out; 2) the pump, after some months ofbearing this unaccustomed load, burns out; 3) scalding hot water, with insufficienttime to cool, boils your prized plant; 4) the machine tries to refill itself and the

hose (with its end lower than the washer) continues to siphon fresh water out untilsomeone shuts off the washer hours later; or 5) the pump doesn't get all of thewater out and clothes stay soggy, or 6), you lift up the hose to move it to a new
http://www.oasisdesign.net/greywater/index.htmhttp://www.oasisdesign.net/greywater/misinfo/index.htm#contentshttp://www.oasisdesign.net/greywater/laundry/index.phphttp://www.oasisdesign.net/greywater/buildersguide/index.htmhttp://www.oasisdesign.net/greywater/buildersguide/index.htm#brancheddrain


20/26



mulch basin before doing a load of laundry and weeks-old fetid grey water rushesbackwards into the machine and onto your clothes.

Preferred practice

TheLaundry to Landscapesystem (page 14) solves all of these problems except the

hot water one. The gravity drum, (page 15) solves all these problems.

Exceptions

As with many of the errors listed here, a certain percentage of installations whichare the perfect embodiment of the error are used for years without any of theseproblems manifesting. The percentage of people who get away with this "error"because of a favorable confluence of characteristics of their washing machineinternal plumbing, site geometry, and use habits is fairly high, as the incidence ofeach individual error is fairly low. If you have an installation like this which has

been working for years, why rock the boat? On the other hand, if you're installinga new system or replacing your old one, why not choose a design which protectsagainst these unhappy possibilities?


Error-Fresh water designs & hardware used for grey water

Most people have more experience with fresh water than grey water. While it mayseem natural to expect grey water to follow the same laws of physics, it doesn't.Here are some examples of the common pitfalls:

U-shaped pipe

Grey water should pass through a rigid "U" shaped pipe, seeking its level just likefresh water. Wrong! Crud in grey water will settle at the bottom of the U, cloggingit.

Preferred practice

2% continuous slope in all rigid lines. This prevents airlocks as well, which plagueinverted U pipes with low pressure fresh and grey water alike.

Exceptions

1) flexible grey water lines won't develop this problem if moved once in a while2) pressurized grey water lines blast the crud through

3) traps are short Us at the bottom of vertical drops that (usually) blast crudthrough
http://www.oasisdesign.net/greywater/index.htmhttp://www.oasisdesign.net/greywater/misinfo/index.htm#contentshttp://www.oasisdesign.net/greywater/laundry/index.php


21/26



Cheap electric valves

Grey water distribution can be controlled elegantly and automatically using $12drip irrigation electric valves. Wrong! Crud in grey water will prevent the valvesfrom closing, grey water will corrode the valves in short order, and grey waterrarely has enough pressure to make this type of valve work right even on the first

day, as they are mostly powered by water pressure.

Preferred practice

1) forget about automated valves2) buy super-expensive electric sewage valves

Filters

This nifty sand/gravel/carbon/reverse osmosis/fill in the blank filter will filter mygrey water just like it does my fresh water so I canWrong! Crud in grey waterwill clog that filter in the blink of an eye.

Preferred practice/Exceptions

Check page 29 for grey water filtration options.

Soaker hose

"I'll just run my grey water through these here soaker hoses"Wrong! Soakerhoses are such a poor technology that they typically have 30% variation in flowwhen brand new and used with fresh waterand they soon clog with all but thecleanest FRESH WATER, let alone grey water.

Corrugated flexible French drain tubing

Corrugated flexible drainpipe has small, rapidly clogging outlets and will collectfestering crud in all it's ups and downs, as well as the corrugations, which is likelyto elevate bacteria and smell levels.

Drip irrigation

See grey water to drip irrigation, below.

http://www.oasisdesign.net/greywater/index.htmhttp://www.oasisdesign.net/greywater/misinfo/index.htm#contentshttp://www.oasisdesign.net/greywater/misinfo/index.htm#drip


22/26



Comparison of how the same size solid

passes through the same flow in 1-1/2",

2", 3" or 4" pipe. Note that while it floats

in the smaller pipe sizes, it is scraping

bottom in the bigger ones. In this case, the

smallest pipe shown provides the best flow.

Error-Combined wastewater designs used

for grey water

Most plumbers have more experience with combinedwastewater (grey water + blackwater) than dedicated

grey water plumbing, and sometimes misapplyprincipals of one to the other.

Here are some examples of the common pitfalls:

Too big of pipe

Combined wastewater generally requires 3 to 4 inchpipe in residences. This is too big forgrey water. Ifyou just ask your plumber to run grey water and

blackwater separately until outside the house, you'vegot a good chance that you'll end up with a three or four inch grey water stub out.How can a pipe be too big? First, it is more awkward, expensive, and burns upvaluable elevation faster. Second, crud in small flows doesn't even flow down it aswell:

Preferred practice

Use 1-1/2 or 2" pipe. This prevents airlocks as well, which plague inverted U pipeswith low pressure fresh and grey water alike.

Exceptions

Huge multifamily or institutional flows.

Distribution in perforated pipe

See Error-Perforated pipe or other indeterminate system for grey waterdistribution


Error: Grey water to drip irrigation

Backyard tinkerers naturally tend to converge independently on the idea of runninggrey water through drip irrigation hardware to distribute it. There is no other wayto achieve 80% irrigation efficiency, short of manually bucketing the water out

plant by plant. The only problem is that it doesn't work. Of the hundreds ofsystems built during the recent (1990's) California drought, every one that I know
http://www.oasisdesign.net/greywater/index.htmhttp://www.oasisdesign.net/greywater/misinfo/index.htm#contentshttp://www.oasisdesign.net/greywater/misinfo/index.htm#distribution


23/26



of has been abandoned (see exceptions, below).

The most common configuration was a surge tank with an inlet filter and a float-actuated sump pump to pressurize the grey water lines. These systems work greatfor the first few weeks, then the filter clogs. At first, the drains are just slow. Thenthere is no denying it; it's time to clean that filter; the pipes are not draining atall. When you remove the filter for cleaning (with rubber gloves, of course; a wise

precaution), you realize the lines are full to the brim; fifty or a hundred feet oftwo-inch pipe's worth of chunky, days-old backed-up grey water comes out in apressurized deluge into the surge tank. Fortunately, you are quick on your feetand you are only lightly spattered. Not more than a third of the solids caught inthe filter have spilled into the surge tank. As you struggle to get your rubbergloves off so you can wipe the flecks off from around your lips and eyes, the sumppump cycles on. Horrified, you stand there paralyzed for a moment as the sumppump charges $300 worth of drip line with last week's split pea soup; by the timeyou wiggle under the crawl space and get the plug pulled on the pump, the dripline is history and the pump is stopped by hair anyway.

Preferred practice

Do something simpler and more robust with less efficiency, or go to a more labor-intensive, less sanitary system like bucketing.

Exceptions

AGWA systems, now out of business, made grey water to drip systems which wereso well designed and built, out of such expensive components, that they actuallyworked. They cost a couple to several thousand dollars. This is not a homebrew-type system. Someone really ought to pick up this business where these folks leftoff.

Update: Jade Mountain (see suppliers) is selling the "Earthstar," which may proveto be a good substitute for AGWA's m100 system.


Error: Automated reuse systems for flushing low usage (e.g.,

residential) toilets

Automated systems for flushing toilets with grey water are complex and expensive.Flushing with untreated grey water will result in fouling of the tank and fetidanaerobic smells (see "Error: storage of grey water"). Treatment is fabulouslyexpensive. The cost for a typical system touted on the web is $10,000. Even at thepunitive water rate of $0.01 a gallon, that's 5 years of 325 flushes a day to

recoup your investment, not counting lost interest, electricity, or systemmaintenance. The $650 Homestead Utilities system (s16), which is the cheapest
http://www.oasisdesign.net/greywater/misinfo/index.htm#storagehttp://www.oasisdesign.net/greywater/index.htmhttp://www.oasisdesign.net/greywater/misinfo/index.htm#contentshttp://www.realgoods.com/renew/index.cfm


24/26



Ive heard of, would take 23 flushes a dayif you had a restaurant it could earnits keep.Extreme economic unfeasibility can indicate extreme ecological unfeasibility; theearth could be way better off if you just wasted the water than if you wasted allthe plumbing, pumps, tanks, filters, and electricity needed to make this sort ofsystem work.

Preferred practice

First, put in a low flush toilet (or a waterless composting toiletsee inside backcover). Then, "if it's yellow let it mellow, if it's brown flush it down." Third, toiletscan be flushed with grey water by simply bucketing it from the bathtub/showerdirectly into the toilet bowl (not the tank, where it will fester). An added plus ofreusing bathtub water in this way is that due to flush volume always being underdirect intelligent control it is always less. Also, in cold climates you get a primitivebut highly effective sort of grey water heat recovery as the bath water sits there

and cools.Once again, the Mexican housewife's system soundly outperforms the USengineer's system! If none of these preferred options appeal to you, you'reprobably better off just forgetting about flushing your toilets with grey water.

Exceptions

Every toilet should have a lid that routes clean drinking water en route to bowl-scouring flush through a basin where it can be used for washing hands.

Multifamily, institutional or any other high useinstallations can benefit from flushing toilets withhighly treated grey water, especially when incorporatedin the original design of the building. If you havehighly treated water already and dont know what todo with it, say from a constructed wetland, it may beworth supplying it to the toilet. An importantadvantage is that toilets need flushing every day,whereas irrigation need is usually seasonal."Clearwater such as air-conditioner drip, reverse-

osmosis water purifier reject water, and fixture warmup water is a natural for flushing toilets. It needs notreatment and can store indefinitely. Steven Coles of Phoenix, Arizona suggeststhat if you have an evaporative cooler, supply the toilet from its reservoir andyoull keep the mineral concentration in the cooler water from rising.


Error: Use of government agencies, trade organizations,engineering firms or salespeople for design of residential grey
http://www.oasisdesign.net/greywater/index.htmhttp://www.oasisdesign.net/greywater/misinfo/index.htm#contentshttp://www.oasisdesign.net/greywater/indoors/index.htm#cascadehttp://www.oasisdesign.net/compostingtoilets/book/index.htm


25/26



water systems

There is very little overlap between the set of practical grey water systems and theset of legal grey water systems. This would seriously hamper the government'sability to give out useful information, if they had it. Because grey water reuse is anew, marginal, rapidly evolving field, it is hard for ponderous bureaucracies to

keep up with. The California grey water law and the pamphlet which explains it areespecially misleading for hardware guidance-see error: using CA grey water law asexample.

Also, there are few practical grey water systems which can be profitably installedprofessionally. It is likely that an established trade organization, engineer, orplumbing company would set you up with an unproven, overkill system adaptedfrom some better known treatment technology. Therefore, you're pretty much onyour own.

Appropriately designed grey water systems are not a very sales-friendly product;way too site-specific, variable, and inexpensive. The world wide web featuresnumerous generic, expensive, prepackaged grey water systems with fantasticclaims, which seem to be better systems for the salesperson than the user.

Preferred practice

So far as I know our two books are the most complete and up to date referencesfor home grey water systems. The designs in our books promise less than in othersourcesbecause our books stick closer to reality. If the answer for your situation

doesn't jump out of our books and web site, call us for a consultation.

Exceptions

For new construction sometimes an over-engineered grey water system is lessover-engineered than conventional treatment. If the administrative authorityrequires it, gritting your teeth and paying up to ten times more for the falseassurance of a brand-name product (which may never have seen success in thefield but still seems safer somehow than you trying something on your own) maybe the best option. Also, the prepackaged grey water system may actually begood, though the odds are against it and I know of none I can confidentlyrecommend (please E mail us if you make or have used a good one).


Error: CA grey water law held up as example to copy

California's new grey water law is an important step and certainly as well done aswas politically possible. Too bad it's a step not quite in the right direction, as it is
http://www.oasisdesign.net/greywater/index.htmhttp://www.oasisdesign.net/greywater/misinfo/index.htm#contentshttp://www.oasisdesign.net/about/contact/feedback.htmhttp://www.oasisdesign.net/catalog/index.htmhttp://www.oasisdesign.net/greywater/misinfo/index.htm#law


26/26


being emulated all over the US and the world. Some of the hardwarerecommendations are questionable. The mini-leachfield system, for example, isdescribed in great detail as if it were a proven technology, but has been installedin no cases I know of and I cant think of any application for which I wouldrecommend it.Unrealistic laws have poor participation rates. Santa Barbara, for example, hasissued approximately 10 permits for grey water systems between 1989 and 1998.There is evidence that during this time of severe drought over 50,000 SantaBarbarans used grey water! There are so many obviously overkill requirementsthat the entire law, including the sensible provisions, is dismissed as a source ofdesign guidance.

Preferred practice

If you're a homeowner, don't follow the law unless you can get a favorableinterpretation or have no choice.

If you are an inspector, sections of the law grant you nearly total discretion toapprove whatever you want. Please exercise this discretion to discount the morepointless sections of the law and allow genuinely well-designed and executedsystems (the sections which grant inspectors this discretion, the deficient sectionsof the law, and suggested revisions are all in the Builder's Grey Water Guide(book), which includes the full text of the law with annotations).If you are a regulator, don't blindly follow California's lead when writing your ownadministrative authorities grey water regulations!A more reasonable regulatory stance would lead to greater participation and areduction in risk from the perpetuation of unregulated systems. Carefully check

over and incorporate the list of needed improvements from the Builder's GreyWater Guide.

Please help distribute this information as widely as possibleit's got a long way togo to catch up with this groundbreaking law!

2009 update: CA itselfis updating it's law.

This information may be reproduced if credit and a link is given. We'd love a copy.

^ Top of page ^ Browse |Catalog

www.oasisdesign.net Copyright Art Ludwig 1997 -2009
http://www.oasisdesign.net/catalog/index.htmhttp://www.oasisdesign.net/index.htm#browsehttp://www.oasisdesign.net/greywater/misinfo/index.htm#tophttp://www.oasisdesign.net/greywater/law/index.htm#californiahttp://www.oasisdesign.net/greywater/law/improve/cpcupc.htmhttp://www.oasisdesign.net/greywater/buildersguide/index.htm

common greywater mistakes and preferred practices

Documents