lecture 2 - water distribution

8/9/2019 Lecture 2 - Water Distribution

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PLANNING the WATER DISTRIBUTION The system must provide adequate supply of water, with

adequate pressure up to the extremities of the system. The safety and quality of water should not be impaired by

defects in the system.

It should be provided with sufficient valves and blow-offs to

allow repair work without undue interruption of service tosome areas, and to allow flushing of the system.

There should be no unprotected open reservoir, or cross

connection with inferior water systems to enter the

distribution system. The water system should be tight against leakage.

The main and branches connection should not be submerged

in surface water, or subjected to any source of

contamination.


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PLANNING the WATER DISTRIBUTION The water system design shall afford effective circulation of

water with minimum number of dead end mains. The system shall be guarded against contamination in any

parts of it resulting from repair works, replacement orextension of the mains.

When new mains are installed, or old mains repaired, theyshould be filled with strong chlorine solution of 40- to60mg/L for at least 24 hours, and then flushed with watersupplied normally from the mains.

As much as possible, water main should be laid above the

elevation of concrete sanitary sewers, or crossover points,and at least 3 meters horizontally from such sanitary sewerwhen they are parallel. Should this be impossible for somereasons, the sewer main must be encased in concrete.


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TYPICAL WATER DISTRIBUTION SYSTEM


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CLASSIFICATION of WATER DISTRIBUTIONPublic water distribution is classified into:

Direct Pressure Distribution A direct-pressure distribution system is one in which no elevated

storage is provided, and the required distribution pressures aremaintained only by pumping facilities.

Obtains its supply of water through a large intake pipe installed inthe lake basin extended down the water

Water is drawn from the lake to a receiving well by force of gravity,passing through the filtration plant

The water inside the reservoir is pumped by a centrifugal, or pistonpump into the water main with sufficient pressure to serve thespecific needs

Indirect Pressure Distribution It is when the water is drawn from a drilled distribution by indirect

pressure

A turbine pump is mounted on top of the standpipe down the wellbelow the water table


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WATER STORAGEAn extremely important element in a water

distribution system is water storage.

System storage facilities have a far-reaching effect on

a systems ability to provide adequate consumer

consumption during periods of high demand. Required water storage capacity in a distribution

system is met by use of elevated or ground level

storage.

Elevated storage, feeds the water distribution system by

gravity flow. Storage which must be pumped into the

system is generally in ground level storage tanks.


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TYPES OF WATER STORAGE

Ground storage

is usually located remote from the treatment plant

but within the distribution system.

is used to reduce treatment plant peak production

rates and also as a source of supply for pumpingto a higher pressure level.

such storage for pumping is common in

distribution systems covering a large area,

because the outlying service areas are beyond the

range of the primary pumping facilities.


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TYPES OF WATER STORAGEGround storage

Types of ground storage tanks or reservoirs are: belowground, partially below ground, or constructed aboveground level in the distribution system,

may be accompanied by pump stations if not built at

elevations providing the required system pressure bygravity. However, if the terrain permits, this designlocation of ground tanks at elevation sufficient forgravity flow is preferred.

Reservoirs are the most common type of waterstorage structure and are categorized as being groundsupported with a flat bottom and a height no greaterthan its diameter.


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TYPES OF WATER STORAGEGround storage

Concrete reservoirs are generally built no deeper than6-7.5 meters (20-25 feet) below ground surface. Ifrock is present, it is usually economical to constructthe storage facility above the rock level.

In a single pressure level systems, ground storagetanks should be located in the areas having the lowestsystem pressures during periods of high water use.

In multiple pressure level systems, ground storage

tanks are usually located at the interface betweenpressure zones with water from the lower pressurezones filling the tanks and being passed to higherpressure zones through adjacent pump stations.


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Elevated Storage

is provided within distribution system to supply

peak demand rates and equalize system pressures.

In general, elevated storage is more effective and

economical than ground storage because of thereduced pumping requirements, and the storage

can also serve as a source of emergency supply

since system pressure requirements can still be

met temporarily when pumps are out of service.


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Elevated Storage The most common types of elevated storage

are elevated steel tanksand standpipes. Inrecent years, elevated tanks supported by

single pedestals have been constructed whereaesthetic considerations are an important partof the design process.

A standpipe is a tall cylindrical tank normallyconstructed of steel or reinforced concrete.

They are ground supported, flat bottom,cylindrical tanks with heights greater than theirdiameter.


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TYPES OF WATER STORAGEElevated Storage

Elevated storage tanks should be located in the areashaving the lowest system pressures during intervals of highwater use to be effective in maintaining adequate systempressures and flows during periods of peak water demand. These are those of greatest water demand or those farthest

from pump stations. Elevated tanks are generally located at some distance from

the pump station(s) serving a distribution pressure level,but not outside the boundaries of the service area, unlessthe facility can be placed on a nearby hill.

Elevated tanks are built on the highest available ground, upto static pressures of 520 kPa (75 psi) in the system, so as tominimize the required construction cost and heights.


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Types of Cold Water Distribution SystemsDirect or Non-storage

All the plumbing fittings are supplied with cold water directfrom the mains.

A cold water cistern is normally used to feed the hot water

supply system though water heaters are available which can be

fitted direct from the mains.

Advantages Less pipe work, smaller or no cistern make it cheaper to install.

Drinking water is available at all draw of points.

Smaller cistern can be sited below the ceiling. In systems without a cistern there is less risk of water

pollution.


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Types of Cold Water Distribution SystemsIndirect or Storage

All plumbing fittings except the kitchen sink is supplied withcold water via a storage cistern, which can also be used to

supply the hot water supply system.

Advantages Cistern provides a reserve of water if supply is interrupted.

Reduced water pressure on taps reduces wear and noise.

Less risk of pollution to drinking water by back siphonage.

Lower demand on the water main.


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COLD WATER DISTRIBUTION IN BUILDINGS

Water is distributed to the household or

buildings by any of the following methods:

Up-feed method

Water is distributed through normal water

pressure from public water main for use in low

rise buildings


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Pneumatic tank

Water is distributed through air pressure coming

from suction tank for use in all tall buildings that

cannot be reached by normal water pressure


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Overhead or Down-feed type

Supplies water to the plumbing fixtures by means

of gravity

The water is pumped to a large tank on top of the

building and distributed to the different fixtures Storage tanks are installed when normal supply of

water from public main is unreliable

Also used when normal pressure is not enough toforce the water to the highest fixture


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WATER PIPE SYSTEM

Water is conveyed from the main source to the

household or buildings by series of pipes: Water main

Refers to the public water connection that are laidunderground along the streets where the house service isconnected

House service pipes Refers to the pipe connection from the water main or any

source of water supply to the building served

Riser pipes

Refers to the vertical supply pipe that extends upwardfrom one floor to the next

Branches Horizontal pipes that serve the faucets or fixtures


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PIPING REQUIREMENTS

The amount of water a pipe will deliver at any one

pressure is a direct result of:

the size of the pipe,

the smoothness of the inside surface and

the pipe length.

The procedures used in selecting pipe size are affected by

whether there is only one building or hydrant being

serviced by the line, or two or more buildings.

Even a small increase in the diameter of the pipe cangreatly increase the amount of water that may flow

through it.


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PIPING REQUIREMENTS

Friction between the inside walls of the pipe and the

moving water creates a force that opposes the flow ofwater through the pipe.

The greater the roughness of the inside of the pipe, the

greater the force caused by friction, and the higher the

pressure required to push the same amount of waterthrough the pipe.

Consequently, pipes with smooth inside surfaces can

deliver more water than pipe walls with rough surfaces

using the same pressure. Pipe connections such as elbows, reducers, tees, unions,

etc., as well as valves, can add greatly to the friction


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TYPES OF PIPES

Galvanized Steel Pipe

Galvanized steel pipe is covered with protectivecoating of zinc that greatly increases its life comparedto black pipe.

It is made in standard 6m lengths with each endthreaded. The pipe is cut and threaded to fit the job.Joints are made by placing a small amount of pipe

joint compound on the pipe threads and screwing onthe fitting.

Galvanized steel pipe is suitable for all piping inside abuilding, but plastic and copper pipe are preferred forunderground installation.

Highly mineralized water greatly reduces the life ofsteel pipe.


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TYPES OF PIPES

Copper Pipe

Copper pipe is available in types "K", "L", and "M". Type "K" is heavy duty - pump suction lines and underground

piping.

Type "L" is standard weight - inside buildings, and

type "M" is light-weight for use only behind walls insidebuildings.

Both types "K" and "L" are available in hard- or soft-tempered form.

Hard-tempered pipe is rigid and comes in 3m to 6m lengths.It is used for exposed piping inside buildings, where it can befit closely to walls or ceilings. It needs very little mechanicalsupport to keep it in position, compared to flexible tubing.

Soft-tempered tubing is excellent for underground use andfor inside existing walls in old buildings.


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TYPES OF PIPES

Plastic Piping

Plastic pipe is available in flexible, semi-rigid, and rigidforms. Flexible pipe is common for undergroundwater piping because of installation ease andeconomy. It is or more in diameter and in coils of100 feet or more.

Solvent welded, or glued, PVC semi-rigid pipe is nowcommon as a result of better and more readilyavailable quality, ditching equipment, and ease of

joining. The joints of polyethylene pipe use nylon orbrass fittings and stainless steel clamps and clamp

screws. Use only pipe fittings that have the National

Sanitation Foundation seal, NSF. It assures that thepipe is safe for use with drinking water.


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PLASTIC PIPES

There are five classes of plastic pipe and fittings

that meet commercial standards established by theASTM for potable household water. Polyethylene (PE)

This flexible or semi-rigid pipe's strength decreases asthe temperature rises, therefore it is for cold-water

lines only. It has pressure ratings between 80 and 160psi. PE pipe is used for hot water heating in concretefloors; temperatures of up to 100F are common forfoot comfort. For this use, however, the best brand ofvirgin plastic rated at 115F should be used. Also,

mixing valves for water temperature control should beinstalled. Lines should also be laid in straight lines toavoid undue stress. PE pipe is available in diameters ofup to 6 inches or larger; and it is joined by threads andclamps.


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PLASTIC PIPES

Polyvinyl Chloride (PVC)

This rigid pipe is available with pressure ratings of 50to 315 psi.

PVC should be used for cold-water only. It is used for some household cold water pipes and

drains and in some permanent irrigation installations. Pipe for pressure water systems should be rated at

least 80 psi. PVC comes in 3m to 6m lengths and common

diameters; and it is joined with a coupling solvent.

It is generally more resistant to crushing or puncturingthan PE pipe, and it will stand slightly highertemperatures.


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PLASTIC PIPES

Chlorinated Polyvinyl Chloride (CPVC)This material is similar to PVC, but it is better for

handling corrosive water at temperatures 40 to

60F above the limits for other vinyl plastics.

It is suitable for hot or cold water lines. Althoughthis type of pipe was developed to handle hot

water, the manufacturer's stress and temperature

limitations should be checked before installing.

Local plumbing codes should be consulted also.


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PLASTIC PIPES

Polybutylene (PB)

This pipe is suitable for both hot or cold waterlines.

Although this type of pipe was developed tohandle hot water, the manufacturer's stress and

temperature limitations should be checked beforeinstalling. Local plumbing codes should beconsulted also.

In both of the classes - PB and CPVC-

manufacturers sometimes make a number ofpipes with different physical characteristics. Careshould be taken in insuring the water systemneeds are met by the pipe selected.


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PLASTIC PIPES

Acrylonitrile Butadene Styrene (ABS)This semi-rigid pipe has pressure ratings between

80 and 160 psi, and is suitable for sewer pipe.


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SIZING OF COLD WATER PIPES

Pipe is categorized based on the wall thickness

(difference between the outside diameter andthe inside diameter), which is termed asschedule, but most pipes are ordered based onthe nominal pipe size, or NPS.

The size of water service pipes is based on themaximum and minimum probable water demand,but in no case shall it be less than 20mmdiameter.

A 20mm service pipe can supply two (2) branches of 12mm diameter pipes deliver water to the house up to 38 l/m sufficient to

serve up to ten (10) fixtures


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PIPE FITTINGS APPLICATIONS Pipe and pipe fittings go hand-in hand.

Just as pipes are used for a variety of residential, public and industrial

applications, so also the pipe fittings. No pipes can be connected without the use of proper fittings and

flanges.

Pipe fittings allow pipes to be installed and connected or joined where

necessary and terminated in the right place.

Pipe fittings include a wide range of products in variousshapes, sizes and materials. With rapid developments in the field of industrial fittings and

continuous research work in this industry, various new products are

manufactured.

Some fittings have certain special features so that they can befabricated on different principles like hydraulics, pneumatic depending

on the end usage.

Fittings include a comprehensive range of products depending on

various applications in which they are applied.


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PIPE FITTINGS BY MATERIALS

Aluminum

Brass

Cast iron

Copper

Malleable

Plastic

Steel


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CATEGORIES OF FITTINGSFittings can be grouped in one of the following

categories:Fittings that extend or terminate pipe runs

Couplings

Adapters

Caps and PlugsFittings that change a pipe's direction

Elbows (ells)

Fittings that Connect two or more pipes

Reducers

Bushings

Flex couplings

Fitting reducers

Adapters


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PIPE FITTINGS BY TYPES

Pi Ad t


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Pipe Adapters Are an extremely important pipe

fitting that extend or terminate pipe

runs. They are used to connect

dissimilar pipes.

Adapters are somewhat similar to

pipe couplings, with the difference

that they connect pipe of different

types, one of which is an IPS (Iron

Pipe Size).

Adapters may have either male or

female IPS threads on one end and

the opposite gender on the other

end, which needs to be welded orsoldered onto a smaller pipe.

Adapters are used in a myriad of

applications but they are typically

used to connect different pipes to

fixtures.


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Bulkhead Fittings Specially designed fittings meant to

allow free flow of liquids in tank, drum

drainage and other plumbingconnections; also used as distribution

outlets in a piping system.

Bulkhead fittings provide full flow of

water and they are also used to attach

flexible pipes with the help of male

adapters. These fittings usually have

left handed threads, which help to keep

the fitting intact and tight while

installing the male adapter.

When used with unions, bulkhead

fittings facilitate the removal of pumpsand accessories.

Bulkhead fittings also come with nuts

and gaskets as accessories. The gaskets

are usually purchased separately.


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Compression fittings are special type of coupling, usually

used to connect two pipes or a pipe to

a fixture or valve.

A compression fitting tightens down a

sleeve or ferrule over a joint to prevent

leakage.

These pipe fittings are very strong and

reliable and can be put on using just a

pair of wrenches; do not require anyheating and go well even with wet

pipes.

Compression fittings are ideal for

household plumbing applications.

Compression fittings are usually madeof materials like:

Brass

Plastic

Copper

Cast Iron

In cases, when compression fittings are

used for joining pipes of two dissimilar

materials, for example PVC and copper, they

should be made of such appropriate

materials that are perfect for the

connection.


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Parts of a Compression Fitting:

The pipe compression fittings consistof three parts:

Compression nut

Compression ring or inner ring or

olive, and Compression seat

A l i f i l d


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Pipe caps act as protective device and are designed

to protect pipe ends of various shapes.

The main purpose of using pipe caps is

to waterproof the connections. They are

also used to close the ends of hydraulic

or pneumatic pipes and tubes.

They are used in the plumbing apparatusof domestic, commercial and industrial

water supply lines, machinery and

processing equipment etc.

They are also fitted on water pump lines

with the sole purpose of removing airblocks.

Pipe caps are highly demanded as an

important category of pipe fittings.

As a large variety of materials are used

for making pipe caps, the buyer should

always take care of the material of the

fitting before going for pipe caps. Some

of the common materials used include:Aluminum

Nylon or polyamide

Polyethylene

Polypropylene

Stainless steel

VinylSilicone rubber etc.


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Common Shapes of pipe caps:Pipe caps are available in variousshapes.

Round

Square

RectangularU Shape Cap

I Shape Cap

Hex Cap etc.

Pipe couplings


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Pipe couplings are fittings that help to extend or

terminate pipe runs. Couplings

extend a run by joining two

lengths of pipe.

They are also used to change pipe

size. They are known as reduced

coupling if they are used to

connect pipes of different sizes. Couplings are also known as repair

couplings. These couplings are

without stops or ridges and they

can be fixed anywhere along the

pipe length for preventing leak of

any kind.

Couplings are of 2 types

Flexible

Rigid


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Pipe elbow fittings are fitting accessories which are used

widely in various industrial sectors in

pipe fitting.

frequently used in pressurized

applications and are available in various

shapes and sizes for use in different

applications.

installed between two lengths of pipeor tube allowing a change of direction,

usually in the 90or 45direction.

Types of pipe elbows are: 90elbow

45elbow

Reducing

Side outlet

Male & female elbow

Street elbow


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Pipe ferrule fittings made of various materials used

especially for joining or binding

one part to another (as pipe

sections).

consist of a circular clamp which

is used to hold together and

attach fibers, wires or posts. It isa type of a ring or cap attached

to an object to protect against

damage, splitting or wear.

A pipe ferrule is also known as a

circular fitting device that is used

to hold the pipes together. Pipe

ferrules are available in various

sizes.


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Pipe Nipple Fittings


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Pipe Nipple Fittings a length of straight pipe with

male threads on both ends.

a connector or a coupling

threaded on both ends.

Pipe nipples are used to allow

plumbing to be connected to a

water heater or other

plumbing. are used to fit straight end hose

or pipe. A combination of pipe

nipples are recommended for

low-pressure discharge andsuction service for various

compatible liquids and not for

compressible products like air,

nitrogen or steam.

Pipe plug Fittings


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p p g g are defined as cap end of fractional

tubes used in a large number of

industries.

These pipe plugs are designed toinsert into the end of tubing to dead-

end the flow.

These pipe plugs come in one piece

body design; easy to replace plugassembly; very easy to maintain and

clean.

The pipe plugs are often plated with

chrome or nickel for a superior finish

and better resistance to corrosion.

Types of pipe plugs are:

Hex

Hollow

square


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Pipe Plug Drive Styles:


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Pipe Union Fittings a type of fitting equipment designed

in such a way to unite two pipes which

can be detached without causing any

deformation to the pipes.

Any kind of small diameter piping

connections requiring a positive seal

and easy assembly as well asdisassembly are made with the help of

pipe union. In other words, the pipe

unions can disjoint two pipes very

easily. They are widely demanded inthe pipe fitting market.


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Pipe Tee Fittings


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Pipe Tee Fittings a type of pipe fitting which is T-shaped having

two outlets, at 90to the connection to the

main line; a short piece of pipe with a lateral

outlet.

Pipe Tee is used to connect pipelines with a

pipe at a right angle with the line. Pipe Tees

are widely used as pipe fittings. They are

made of various materials and available invarious sizes and finishes.

Pipe tees are extensively used in pipeline

networks to transport two-phase fluid

mixtures.

Types of pipe tees are: Bullhead

Female branch

Male & female run

Male

Reducing tee


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Pipe wye Fittings are used to allow one pipe to join

another pipe at some degree or

angle.

As the name suggests, the pipe wyes

are Y-shaped pipe fitting devices.

Pipe wyes are similar to pipe tees.

The only difference is in that thebranch line is angled to reduce

friction which could hamper the

flow. The pipe connection is typically

at a 45-degree angle rather than a

usual 90-degree angle.

Types of pipe wyes: Standard

Reducing


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PIPE JOINT TYPES


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Pipe Joint

Required to connect pipe to itself, a fitting or topiece of equipment

The joint type selected for a particular application

depends on: Pipe material and wall thickness

Pipe contents

System pressure

System temperature Disassembly requirements

Applicable plumbing codes


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CAULKED JOINT A type of joint used for cast-iron pipe

having hub-and-spigot ends. After the spigot-end of one pipe is

placed inside the hub-end of the other,

a rope of oakum or hemp is packed into

the annular space around the spigot

end until the packing is about 1 inch

(2.5 cm) below the top.

Then molten lead is poured into the

annular space on top of the rope.

Finally, the lead is pounded farther into

the joint with a caulking iron.


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COMPRESSION GASKET JOINT A type of joint used only for pipe having

hub-and-plain ends.

Are flexible pressure joints suitable for

gravity drainage and pressurized liquid

systems compatible with the pipe and

gasket.


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COMPRESSION COUPLING

JOINT Rigid non-pressure joints used to join

plain end drainage pipes

Suitable for gravity drainage systems


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THREADED JOINT Can be used for any pipe with walls thick

enough to have threads cut

This rigid pressure joint is generally limited

to 100mm pipe as it is difficult to turn

large pipe Threaded ends come tapered (for

plumbing and utility pipes per ANSI B-2.1)

and standard (for process pipe systems).


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SOLVENT CEMENT JOINT This rigid pressure joint can be used only

with plastic pipe

Each plastic requires a specific

solvent/cement ratio combination

recommended by the manufacturer.

A joint created with solvent cement looks

like a soldered joint, but the cement is

used to soften and dissolve the plasticafter which it hardens into a

homogeneous joint.

SOLDERED AND BRAZED JOINT


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SOLDERED AND BRAZED JOINT Is a rigid pressure-type joint used to join

copper and copper alloy pipes and fittings

The distinction between soldering and

brazing is the temperature required to melt

the filler metal that enters the joint by

capillary action.

In case of brazing, the filler metal (brazing

metal) should have the melting point more

than 450oC, while soldering requires less thanthat. Brazing produces joints stronger than

the pipe itself.

Flux is required for solder and some types of

brazing filler metal but is prohibited for use

with gases installed in health care facilities Filler metal for soldering consists of 50% tin

and 50% lead. No lead is permitted for

potable water systems.

Soldered joints are used for relatively low-

pressure applications


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FLARED JOINT This rigid pressure joint is used for

relatively low-pressure applications onsmall diameter pipes made of soft copper

or other metals.

They are commonly used with capillary

piping in laboratories and small diameter

underground water piping. Proprietary types of flared fittings are

available for high-pressure applications.


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WELDED JOINT Rigid pressure joint formed as butt-fused

joint or socket weld.

Butt-fused joints are created by meltingprepared end metal pipes or square end

plastic pipes, then butting them together

and fusing them, which forms a

homogeneous joint upon hardening.

Metal pipe ends are externally heated

and melted with an electric arc or flame

and filler metal added to form the joint.

For plastic pipe, the ends are melted

separately and brought together to form

the joint with the use of a special

machine. For a socket weld, a plain pipe end Is

placed inside a socket and the end of the

socket fitting is welded to the exterior of

the pipe to form a rigid joint.


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FLANGED JOINT A rigid pressure joint consisting of two

companion flanges, bolted together

and made leak-proof by means of agasket.

Flanges can be installed on the pipe

end by welding, threading or brazing.


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HEAT-FUSED JOINT A rigid pressure joint used only for

thermoplastic pipes

A special socket fitting has resistanceheating wire embedded near the

outer edge facing the pipe to be

joined, complete with pigtails

extended outside the fitting.

An external electrical power source is

connected to the wire pigtails to

generate the heat to melt both the

inside of the socket and the outside of

the pipe in the area where the wire isembedded.

When the material is cool, a rigid joint

has been formed and the pigtails are

cut off.

SPLIT COUPLING JOINT


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SPLIT-COUPLING JOINT This joint requires two types of pipe

end preparation, roll grooving and cut

grooving. The latter method is stronger, but the

roll grooves must be used when the

pipe is too thin for a groove.

These rigid pressure type joints are

well-suited for both pressure andnon-pressure lines.


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WATER SERVICE FITTINGS andDEVICES


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Valves Valve is an equipment designed to stop or regulate

flow of any fluid (liquid, gas, condensate, stem, slurryetc.) in its path.

Valves are categorized depending on their

applications like isolation, throttling and non-return.

It is installed in the piping system based on itsrequirement.

Various type of valves are available depending upon

the type of construction.

The two principal types of valves used to stop the

flow of water in water supply systems are gate valves

and globe valves.

Gate Valves


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Gate Valves

It is operated by raising and lowering a double-faced wedge-

shaped gate.

When the valve is closed, the two faces of the gate are

tightly pressed against the seats, thus effecting a double

seal.

The chief advantages of a gate valve are:

its tight seal

full size straightway opening, which offers no greater resistance

to the flow of water than would an ordinary pipe coupling or

other fitting of equal length.

Either end of this make of gate valve may be used as the

inlet, although there are some makes of gate valves that are

single seated or have only one gate face.

Such valves should be screwed on a pipe with the valve face

to the pressure.


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Globe Valves


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Globe Valves One of the types of valve most commonly used for water

supply systems.

This type of valve has an inlet and outlet end, and a valve

disk, a, that closes against the pressure.

The valve is operated by lowering the disk, a, until it

presses firmly and evenly on the valve seat and thus cuts

off the flow of water. By turning the valve stem to the left,thus raising the valve disk from its seat, the water is

turned on.

Instead of an interchangeable soft disk, some globe valves

have a brass disk that closes on a brass seat. Such valves seldom remain water tight more than a few

months and cannot be repaired as easily and inexpensively as

can soft disk valves; therefore, it is a matter of economy to use

soft seat valves.

Globe Valves


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Globe Valves The principal objections to the use of globe valves are:

the opening through the seat of the valve is not the full area of

the corresponding size of pipe, and therefore not only restricts

the flow but offers considerable frictional resistance

the opening is not straightway, consequently it offers

additional frictional resistance to the flow of water.

they also, when placed on horizontal pipes, form traps thatkeep the pipes half full of water when the pipes are

drained. This latter objection, however, can be overcome by turning the

valve on its side, so the stem will be nearly horizontal. In this

position the opening in the valve seat is as low as the bottomof the pipe and permits all water to drain out.


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Lift Check Valves


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A check valve is an automatic valve that opens to the pressure of

water on one side but closes tightly when pressure is applied to

the opposite end of the valve. A check valve should be used where water should always flow in

one direction and there is a possibility of a reverse flow.

There are two common types of check valves; lift check valves,

and swing check valves.

In a lift valve, the check seats by gravity when pressure in the system

on both sides of the valve is equal.

When pressure on the inlet end of the valve exceeds that in the outlet,

the pressure unseats the check from the seat and permits water to

flow through the valve.

If there is an excess of pressure on the outlet end of the valve, the

pressure will the more tightly seat the check and prevent any water

from passing back through it.

Check valves are made both for vertical and for horizontal pipes.


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LIFT CHECK VALVE

Swing Check Valve


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Swing Check Valve It derives its name from the fact that the metal flap, a,

yielding to the pressure of water, swings on the pivot

and thus presents a straightway opening for the flow

of water.

This type of check valve compares with the lift check

valve about as a gate valve compares with a globevalve.

The swing check valve offers less resistance to the

flow of water through it and has a straightway

opening of almost the full size of the valve. In the lift check valve, on the contrary, the water must pass

through a reduced opening in the valve seat and must

make two right angle turns while doing so.


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Pressure Regulators


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Pressure Regulators Apparatus for controlling or decreasing the pressure of

water within a building and thus relieving the system of

excessive strain. By their use, the static pressure within a building can be

maintained at a pressure of 15, 25 or more pounds, while the

static pressure in the street might exceed 100 pounds; at the

same time, the volume of water or the pressure of the waterwhile running will not be affected by the pressure

reducing valve


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RELIEF VALVES


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RELIEF VALVES Relief valves are automatic valves used on system lines and

equipment to prevent over pressurization.

Most relief valves simply lift (open) at a preset pressure and reset

(shut) when the pressure drops only slightly below the lifting

pressure.

System pressure simply acts under the valve disk at the inlet

of the valve. When system pressure exceeds the force exerted by the valve

spring, the valve disk lifts off its seat, allowing some of the system

fluid to escape through the valve outlet until system pressure is

reduced to just below the relief set point of the valve.

The spring then reseats the valve.

RELIEF VALVES


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RELIEF VALVES An operating lever is provided to allow manual cycling of the

relief valve or to gag it open for certain tests.

Virtually all relief valves are provided with some type of device to

allow manual cycling.

Other types of relief valves are the high-pressure air safety

relief valve and the bleed air surge relief valve.

Both of these types of valves are designed to open completely at aspecified lift pressure and to remain open until a specific reset

pressure is reachedat which time they shut.

Many different designs of these valves are used, but the same

result is achieved.


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F ll P F


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Fuller Pattern Faucets A type of faucet for low

pressure work. This type of cock is quick closing

and closes with the pressure, a

rubber packing, a, effecting the

seal. On account of the quickness

with which this kind of cock can

be closed, each supply pipe to

which they are connected

should be provided with an air

chamber and they should not

be used on high pressure work.

Ground Key Cocks


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May be either stop cocks for controlling water in a pipe,

or faucets for drawing water at a fixture.

The only difference is in their exterior appearance, the principlesof construction and operation being the same for both patterns.

The plug, a, is ground to a watertight fit in the cock, b, and

water is turned on and off by giving a one-quarter turn to

the lever, c.

The principal objection to this kind of a cock is that the constant

wearing of the plug and cock every time the water is turned on

or off, soon causes the cock to leak, and the leak can only be

repaired by re-grinding the plug, which is a tedious and rather

expensive undertaking. Another objection is the quickness with which this type of cock

shuts off the water. Where the water pressure is high, this might

cause serious damage to pipes and fixtures.


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GROUND KEY COCK

Compression Cocks


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A compression cock is used at kitchen

sinks. In construction it is quite similar to

a globe valve and, like one, it closesagainst the pressure.

The core, a, of a compression cock is

fitted with a soft disk packing, b, which

can be easily renewed when the cock

leaks. They are also fitted with a rubber

packing, c, or in some cases with a

ground joint to prevent water spouting

out around the compression stem. Compression stop cocks should be fitted

with an auxiliary stuffing box around the

stem to withstand the back pressure they

are subjected to.

Self Closing Faucets


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Self-Closing Faucets Water can be drawn from a self-

closing bibb only while it is heldopen; the moment the hand is

removed, the faucet is

immediately closed by a spring

provided for that purpose.

When the stem, a, is turned to

the left it raises the block, b,

thus compressing the spring, c,

which, as soon as the pressure

is removed, returns to its

original shape, thus closing the

faucet.


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Water hammer (or hydrostatic shock) is a noisy pipe problem that occurs when valves are

shut off quickly. You may hear banging water pipes, or clanging, rattling, or rumbling


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q y y g g p p , g g, g, g

noises in the water piping when a plumbing fixture, sink, or clothes washer turns off.

Water hammer can damage pipe connections and result in leakage.

Water hammer works like this: water passing through a pipe has momentum or velocity.

When the valve is shut quickly, the momentum of the water carries it into the valve withconsiderable force.

Since water is essentially incompressible, a large pressure is built up against the valve, and

there is low pressure upstream in the pipe. The high-pressure water wants to flow to the

low-pressure area.

This happens so quickly that a small vacuum is created against the valve as the water

moves away from it. This can result in cavitation as the water is pulled back against the

valve a second time.

This continues back and forth in slowly diminishing shock waves. Pressures up to 600 psi

(some sources say 1000 psi) can result from water traveling up to 3,000 miles per hour, for

very short periods.

Water hammer can result in loud noises in supply plumbing pipes. Water hammer only

occurs as valves are closed. If a valve is closed slowly, and the noise does not occur, one

can be sure that water hammer is the problem.

Water hammer is common with quick-closing electrically operated valves on appliances

such as washing machines and dishwashers Air chambers can be installed to control water

lecture 2 - water distribution

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