RAIN WATER HARVESTING

Presented by:- plumbing welfare association.

office:- Dharm plaza plot no-304/305 near R.B.L

bank n-3cidco jalna road aurangabad

Email:-pcwa@gmail.com Apsc@gmail.com

cont:-

9579555255,97303377,9022220073,9096142142

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Rainwater harvesting (RWH): technology used for collecting

and storing rainwater for human use from rooftops, land

surfaces or rock catchments.

One of the world’s most important ancient water supply

techniques (practiced for more than 4,000 years), is beginning

to enjoy a resurgence in popularity.

Rainwater is an important water source in many areas with

significant rainfall but lacking any kind of conventional,

centralised supply system.

Introduction (1)

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Why?

Economics• Reduces water bills

• Reduced water demand - water supply utility saves money on treatment and pumping

• Reduces cost of infrastructure necessary for water supply

Environment• Energy saved – no pumping of water to our homes

• If water is hard, adding soft rainwater improves water quality

• Improves groundwater situation

• Reduces demand for water at city/village level

Other• Simple, cost-effective, easy to construct and maintain

• Viable in urban and rural areas, slums, low income housing, apartments

• Can offset the need for multipurpose river projects

What is the solution ?

• Rain water is the ultimate source of fresh

water

• Potential of rain to meet water demand is

tremendous

• Rain water harvesting helps to overcome

water scarcity

• To conserve ground water the aquifers must

be recharged with rain water

• Rain water harvesting is the ultimate answer

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Typical Domestic Rainwater Harvesting

System

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Ground Catchment System

Source: ENSIC (1991)

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Use of Harvested Rainwater

Non-potable purposes (mainly in urban areas)

- Gardening

- Flushing

- Washing clothes/cars

Potable purpose after ensuring quality

(mainly in rural and peri-urban areas)

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Small-scale rainwater harvesting systems and

uses

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The initial cost (mainly of storage tank) may prevent a

family from installing a RWH system.

The water availability is limited by the rainfall intensity

and available roof area.

Mineral-free rainwater has a flat taste, which may not be

liked by many.

The poorer segment of the population may not have a

roof suitable for rainwater harvesting.

Domestic RWH will always remain a supplement and not a

complete replacement for city-level piped supply or supply

from more ‘reliable’ sources.

Limitations of RWH

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Rainfall quantity (mm/year)

Rainfall pattern

Collection surface area (m2)

Runoff coefficient of collection (-)

Storage capacity (m3)

Daily consumption rate (litres/capita /day)

Number of users

Cost

Alternative water sources

Factors affecting RWH system design

Reasons of Shortage of Water• Population increase

• Industrialization

• Urbanization

• (a) Increase in per capita utilization

• (b) Less peculation area

• In places where rain fed/ irrigation based crops

are cultivated through ground water

• Decrease in surface area of Lakes, talab, tanks etc.

The typical roof top rain water

harvesting system comprises

• Roof catchment

• Gutters

• Down pipe & first flushing pipe

• Filter Unit

• Storage Tank

Roof catchment

The roof of the house is used as the catchment

for collecting rain water. The style construction

and material of the roof effect its suitability as a

catchment, Roofs made of corrugated iron sheet ,

asbestos sheet, Tiles or Concrete can be utilized

for harvesting the rain water

Gutters

Gutters are channels fixed to the edges of

roof all around to collect & transport the

rainwater from the roof. Gutters can be

made in semi-circular and rectangular

shape with cement pipe, plain galvanized

iron sheet, PVC pipes, bamboos etc. Use of

locally available material reduce the overall

cost of the system

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Gutters - Shapes and Configurations

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Gutters and Hangers

25http://www.eng.warwick.ac.uk/DTU/pubs/wp/wp55/8gutter.html

Plastic sheet guttering

First Flush Pipe

Debris, dust & dirt collect on the roof

during non rainy periods when the first rain

arrive. A first flush system arrangement is

made to avoid the entering unwanted

material into the Filter media & storage

tank. This is a simple manually operated

arrangement or semi-automatic system

with a valve below the ‘T’ junction

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First flush system (3)

Developed by Khon Kaen University, Thailand

Filter Unit

The filter unit is a container or

chamber filled with filter media such as

coarse sand, charcoal, coconut fiber,

pebbles & gravels to remove the debris &

dirt from water that enters the tank. The

filter unit is placed over the storage tank or

separately. It may be of Ferro cement filter

unit, Aluminum, Cement rings or Plastic

bucket etc.

Storage Tank

It is used to store the water that is collected from the roof through filter. For small scale water storage plastic buckets, jerry cans, clay or cement jars, ceramic jars, drums may be used. For larger quantities of water, the system will require a bigger tank with cylindrical or rectangular or square in shape constructed with Ferro cement or cement rings or plain cement concrete or reinforced cement concrete or brick or stone etc. The storage tank is provided with a cover on the top to avoid the contamination of water from external sources. The storage tank is provided with pipe fixtures at appropriate places to draw the water to clean the tank & to dispose of extra water. A provision for keeping the vessel to collect the water is to be made.

Size of Storage Tank• Based on

• No. of person in the House hold

• Per capita water requirement

• No. of days for which water is required

• Example

• Drinking water requirement for a household with

5 family members, period 8 months & 6 lpcd

• = 5x 180x 6

• = 7200 Liters

Water available from Roof

Annual rainfall (in mm) x roof area (in sq. m) x co-

efficient of run off for roof

co-efficient of run off

GI sheet 0.9

Asbestos 0.8

Tiled 0.75

Plaster on bricks/ Concrete 0.7

Water available from roof top 800mmx 20

sq.m=12800 Liters per annum

Water available from Roof

continued……Size of Tank =1.2 m dia 1.8 m height

No. of Tanks 4

Volume of Tanks 3.14x1.2x1.2x1.5/4

2.03 cum

2000 liters

Volume of of 4 tanks =

4x2000

8000 Liters

(this can be designed as per requirement)

Cost of Material for Tank1. Cement 8 bags*Rs. 140.00

1120.00

2. Grit .25 Cum 200.00

3. Sand .4 Cum 100.00

4. Perforated Cement rings 5 No. 1000.00

5. P/fabricated Cement rings 4 No. 400.00

6. PVC pipe 63mm dia.*10M 200.00

7. P/fabricated Asbestos 10mm dia.*10mm

Gutters250.00

8. Mason/ Labor charges. 1000.00

9. Transportation 130.00

Total4400.00

Cost of Material for Filtration Tank

1. P/fabricated cement rings 5*Rs. 40.00200.00

2. Cement 2 bags*Rs. 140.00280.00

3. Sand 2 bags 50.00

4. Grit 4 bags 50.00

5. Charcoal 20 Kg*Rs. 8.00160.00

6. Sand for Plastering 4 bags 100.00

7. Mason/ Labor500.00

8. White washing 40.00

9. Transportation 50.00

Total1430.00

Total Cost of construction Rs. 4400.00+Rs.

1430.00= Rs. 5830.00

The cost on O/ M-

White washing 100.00

Water testing 200.00

(2 times a year)

300.00

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A solid secure cover to keep out insects, dirt and

sunshine

A coarse inlet filter to catch leaves etc.

A overflow pipe

A manhole, sump and drain for cleaning

An extraction system that does not contaminate the

water e.g. tap/pump

A soakaway to prevent split water forming puddles

near the tank.

Additionally features

- sediment trap or other foul flush mechanism

- device to inside water level in the tank

Requirements for Storage System

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Underground lime and bricks cistern

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The quality of rainwater is relatively good but it is

not free from all impurities.

Analysis of stored rainwater has shown some

bacteriological contamination.

The rainwater is essentially lacking in minerals,

the presence of which is considered essential in

appropriate proportions.

Cleanliness of roof and storage tank is critical in

maintaining good quality of rainwater.

The storage tank requires cleaning and

disinfection when the tank is empty or at least

once in a year.

Quality of Rainwater (1)

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The extraction system (e.g. taps/faucets, pumps) must

not contaminate the stored water.

The first run off from the roof should be discarded to

prevent entry of impurities from the roof.

Some devices and good practices have been suggested

to store or divert the first foul flush away from the storage

tank.

In case of difficulties in the rejection of first flow, cleaning

of the roof and gutter at the beginning of the rainy season

and their regular maintenance are very important to

ensure better quality of rainwater.

Quality of Rainwater (2)

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The simple operation and maintenance of RWH

systems is one of the most attractive aspects of the

technology.

The extent of maintenance required by a basic

privately owned household RWH system includes

- Regular cleaning of the roof tops and gutters

- Frequent cleaning of storage tanks

- Inspection of gutters and feeder pipes and valve

chambers to detect and repair leaks

When ground catchment is used for collection and/or

ground tank is used for storage, proper fencing of both

is recommended to keep the children and animals away, thus

avoiding contamination and risks of falling into the tank.

Operation and maintenance

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