roof top rainwater harvesting

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MUKESH PATEL SCHOOL OF TECHNOLOGY MANAGEMENT

& ENGINEERING

SHIRPUR, D IST . DHULIA (M.S) - 425405 .

ROOF TOP RAINWATER HARVESTING

SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE

2 ND Y EAR B.T ECH . T RIMESTER V

BY

SNEHAL JAIN

Roll No: 912

(SAP ID)

2011 –

2012



Department of CIVIL Engineering

CERTIFICATE

This is to certify that Mr./Ms. Snehal Jain with Roll No.: 912 , Branch: Civil of

Second Year B.Tech Course has satisfactory completed his seminar report in the topic of

SEISMIC ANALYSIS AND DESIGN FOR UNDERGROUND STRUCTURES during

Trimester –

V under the guidance of Professor Mr. Hemant Wagh in academic year

2011-12 In accordance with the syllabus prescribed by the NMIMS University, Mumbai .

Submission Date : -

Place :- Shirpur Signature of Signature of Signature of

Dean Guide faculty HOD



ABSTRACT:-

concept of water harvesting is not new for India. Water harvesting techniques had been evolved

and developed centuries ago.

Living creatures of the universe The paper outlines rainwater harvesting is being frequently used

these days, however, the are made of five basic elements, viz., Earth, Water, Fire, Air and Sky,

Obviously, water is one of the most important elements and no creature can survive without it.

Despite having a great regard for water, we seem to have failed to address this sector seriously.

Human being could not save and conserve water and it sources, probably because of its

availability in abundance. But this irresponsible attitude resulted in deterioration of water bodies

with respect to quantity and quality both. Now, situation has arrived when even a single drop of

water matters. However. “Better late than never", we have not realized the seriousness of this

issue and initiated efforts to overcome those problems.

Ground water resource gets naturally recharged through percolation. But due to indiscriminatedevelopment and rapid urbanization, exposed surface for soil has been reduced drastically with

resultant reduction in percolation of rainwater, thereby depleting ground water resource.

Rainwater harvesting is the process of augmenting the natural filtration of rainwater in to the

underground formation by some artificial methods. "Conscious collection and storage of

rainwater to cater to demands of water, for drinking, domestic purpose & irrigation is termed as

Rainwater Harvesting”.



INDEX:-

1. Introduction…………………………………………………………………………………..…6

1.1 what is roof to p rainwater harvesting………………………………………………………….71.2. needs of rainwater harvesting…………………………………………………………….......8

1.3. why rain water harvesting…………………………………………………………..………...8

3. application areas………………………………………………………………………………...9

4. components of rainwater harvesting………….………………………………..……………...10

4.1 catchments.....………………………………………..………………………………….……11

4.2 coarse mesh………..………………………………………………………...………………12

4.3 gutters.…………………………………………………………………………………… .....12

4.4conduits……...………………………………………………………………………………..13

4.5first-flushing……………………………………..……………………………………………14

4.6 filters………………………..………………………………………………………………..15

4.6.1 charcoal water filters……………………………………………………….………………16

4.6.2 sand filters…………………………………………………………………………… ..…...16

4.6.3 filters for large rooftops……………...…………………………………………………….17

5. method of rooftop rainwater harvesting……………………………………………………….17

5.1 storage use……………………………………………...…………………………………….18

5.2 recharging of groundwater acquifiers…………………….………………………………….18

5.3 recharging of borewells……………………………………………………………………....19

5.4 recharging of pits…………………..………………………………………………………...19

5.5 recharging of shafts…………………………………………………………………………..20

5.6 recharge of dug wells……………….………………………………………………………..20

5.7 recharge of trenches……………………………………………………………………….....21

6. conclusion……………………………………..………………………………………………22

7. references……………...………………………………………………………………………23



INTRODUCTION:-

WHAT IS ROOF TOP RAIN WATER HARVESTING

Rooftop Rain Water Harvesting is the technique through which rain water is captured from the

roof catchments and stored in reservoirs. Harvested rain water can be stored in sub-surface

ground water reservoir by adopting artificial recharge techniques to meet the household needsthrough storage in tanks.

The Main Objective of rooftop rain water harvesting is to make water available for future use.Capturing and storing rain water for use is particularly important in dryland, hilly, urban and

coastal areas. In alluvial areas energy saving for 1m. rise in ground water level is around 0.40

kilo watt per hour.



Fig: Rooftop rainwater harvesting system

NEED FOR ROOFTOP RAIN WATER HARVESTING

1. To meet the ever increasing demand for water

2. To reduce the runoff which chokes storm drains3. To avoid flooding of roads.

4. To augment the ground water storage and control decline of water levels

5. To reduce ground water pollution6. To improve the quality of ground water

7. To reduce the soil erosion

8 To supplement domestic water requirement during summer, drought etc.

Why rainwater harvesting:-

In many regions of the world, clean drinking water is not always available and this is only

possible with tremendous investment costs and expenditure. Rainwater is a free source and

relatively clean and with proper treatment it can be even used as a potable water source.

Rainwater harvesting saves high-quality drinking water sources and relieves the pressure on

sewers and the environment by mitigating floods, soil erosions and replenishing groundwater



levels. In addition, rainwater harvesting reduces the potable water consumption and

consequently, the volume of generated wastewater.

Application areas :-

Rainwater harvesting systems can be installed in both new and existing buildings and harvested

rainwater used for different applications that do not require drinking water quality such as toilet

flushing, garden watering, irrigation, cleaning and laundry washing. Harvested rainwater is also

used in many parts of the world as a drinking water source. As rainwater is very soft there is also

less consumption of washing and cleaning powder. With rainwater harvesting, the savings in

potable water could amount up to 50% of the total household consumption.

Criteria for selection of rainwater harvesting technologies

Several factors should be considered when selecting rainwater harvesting systems for domesticuse:

• type and size of catchment area

• local rainfall data and weather patterns

• family size

• length of the drought period

• alternative water sources

• cost of the rainwater harvesting system.

When rainwater harvesting is mainly considered for irrigation, several factors should be taken

into consideration. These include:

• rainfall amounts, intensities, and evapo-transpiration rates

• soil infiltration rate, water holding capacity, fertility and depth of soil

• crop characteristics such as water requirement and length of growing period

. Components of a rooftop rainwater harvesting system

Although rainwater can be harvested from many surfaces, rooftop harvesting systems are most

commonly used as the quality of harvested rainwater is usually clean following proper

installation and maintenance. The effective roof area and the material used in constructing the

roof largely influence the efficiency of collection and the water quality.

Rainwater harvesting systems generally consist of four basic elements:(1) a collection (catchment) area

(2) a conveyance system consisting of pipes and gutters

(3) a storage facility, and

(4) a delivery system consisting of a tap or pump.



COMPONENTS OF A RAINWATER HARVESTING SYSTEM :-

A rainwater harvesting system comprises components of various stages - transporting rainwater through

pipes or drains, filtration, and storage in tanks for reuse or recharge. The common components of a

rainwater harvesting system involved in these stages are illustrated here.

Catchments: The catchment of a water harvesting system is the surface which directly receives the

rainfall and provides water to the system. It can be a paved area like a terrace or courtyard of a building,

or an unpaved area like a lawn or open ground. A roof made of reinforced cement concrete (RCC),

galvanised iron or corrugated sheets can also be used for water harvesting.

Coarse mesh: at the roof to prevent the passage of debris.

3.Gutters: Channels all around the edge of a sloping roof to collect and transport rainwater to the storage

tank. Gutters can be semi-circular or rectangular and could be made using:

Locally available material such as plain galvanised iron sheet (20 to 22 gauge), folded to

required shapes.



Semi-circular gutters of PVC material can be readily prepared by cutting those pipes into two

equal semi-circular channels.

Bamboo or betel trunks cut vertically in half.

The size of the gutter should be according to the flow during the highest intensity rain. It isadvisable to make them 10 to 15 per cent oversize.

Gutters need to be supported so they do not sag or fall off when loaded with water. The way in

which gutters are fixed depends on the construction of the house; it is possible to fix iron or

timber brackets into the walls, but for houses having wider eaves, some method of attachment to

there after is necessary.

Fig 6: A clean PVC gutter to catch every drop of rain



4. Conduits

Conduits are pipelines or drains that carry rainwater from the catchment or rooftop area to the

harvesting system. Conduits can be of any material like polyvinyl chloride (PVC) or galvanized

iron (GI), materials that are commonly available.

The following table gives an idea about the diameter of pipe required for draining out rainwaterbased on rainfall intensity and roof area:

Sizing of rainwater pipe for roof drainage :-

Diameter

Of pipe

(mm)

Average rate of rainfall in mm/h

50 75 100 125 150 200

50 13.4 8.9 6.6 5.3 4.4 3.3

65 24.1 16.0 12.0 9.6 8.0 6.0

75 40.8 27.0 20.4 16.3 13.6 10.2

100 85.4 57.0 42.7 34.2 28.5 21.3

125 - - 80.5 64.3 53.5 40.0

150 - - - - 83.6 62.7

mm/ h - millimeters per hour; m – meters

5. First-flushing :-

A first flush device is a valve that ensures that runoff from the first spell of rain is flushed out

and does not enter the system. This needs to be done since the first spell of rain carries a

relatively larger amount of pollutants from the air and catchment surface.



Source: A water harvesting manual for urban areas

6. Filter :-

The filter is used to remove suspended pollutants from rainwater

collected over roof. A filter unit is a chamber filled with filteringmedia such as fibre, coarse sand and gravel layers to remove debris

and dirt from water before it enters the storage tank or recharge

structure. Charcoal can be added for additional filtration.

i) Charcoal water filter

A simple charcoal filter can be made in a drum or an earthen pot. Thefilter is made of gravel, sand and charcoal, all of which are easily

available.



(ii) Sand filters

Sand filters have commonly available sand as filter media. Sand filters

are easy and inexpensive to construct. These filters can be employed for

treatment of water to effectively remove turbidity (suspended particles

like silt and clay), colour and microorganisms.In a simple sand filter that can be constructed domestically, the top layer

comprises coarse sand followed by a 5-10 mm layer of gravel followed

by another 5-25 cm layer of gravel and boulders.



ii. a)Dewas filters:-

Most residents in Dewas, Madhya Pradesh, have wells in their houses. Formerly, all that those

wells would do was extract groundwater. But then, the district administration of Dewas initiateda groundwater recharge scheme. The rooftop water was collected and allowed to pass through a

filter system called the Dewas fillter, designed by Mohan Rao , district collecter of Dewas, and

engineers of the rural engineering services. The water thus filtered is put into the service

tubewell.

The filter consists of a polyvinyl chloride (PVC) pipe 140 mm in diameter and 1.2m long. Thereare three chambers. The first purification chamber has pebbles varying between 2-6 mm, the

second chamber has slightly larger pebbles, between 6 and 12 mm and the third chamber has the

largest - 12-20 mm pebbles. There is a mesh at the outflow side through which clean water flows

out after passing through the three chambers. The cost of this filter unit is Rs 600.

http://www.rainwaterharvesting.org/People/innovators-urban.htm#mmoh






Filter for large rooftops:-

When rainwater is harvested in a large rooftop area, the filtering system should accommodate theexcess flow. A system is designed with three concentric circular chambers in which the outer

chamber is filled with sand, the middle one with coarse aggregate and the inner-most layer with

pebbles



This way the area of filtration is increased for

sand, in relation to coarse aggregate and pebbles.Rainwater reaches the centre core and is

collected in the sump where it is treated with few

tablets of chlorine and is made ready for

consumption.



Methods of Roof Top Rainwater Harvesting

Storage of Direct use

In this method rain water collected from the roof of the building is diverted to a storage tank. The

storage tank has to be designed according to the water requirements, rainfall and catchment

availability. Each drainpipe should have mesh filter at mouth and first flush device followed by

filtration system before connecting to the storage tank. It is advisable that each tank should have

excess water over flow system.

Excess water could be diverted to recharge system. Water from storage tank can be used for

secondary purposes such as washing and gardening etc. This is the most cost effective way of

rainwater harvesting. The main advantage of collecting and using the rainwater during rainy

season is not only to save water from conventional sources, but also to save energy incurred on

transportation and distribution of water at the doorstep. This also conserve groundwater, if it is

being extracted to meet the demand when rains are on.

Recharging ground water aquifers:-

Ground water aquifers can be recharged by various kinds of structures to ensure percolation of

rainwater in the ground instead of draining away from the surface. Commonly used recharging

methods are:-

a) Recharging of bore wells

b) Recharging of dug wells.

c) Recharge pits

d) Recharge Trenches

e) Soak ways or Recharge Shafts

f) Percolation Tanks



Recharging of bore wells:-

Rainwater collected from rooftop of the building is diverted through drainpipes to settlement or

filtration tank. After settlement filtered water is diverted to bore wells to recharge deep aquifers.

Abandoned bore wells can also be used for recharge.

Optimum capacity of settlement tank/filtration tank can be designed on the basis of area of

catchement, intensity of rainfall and recharge rate as discussed in design parameters. While

recharging, entry of floating matter and silt should be restricted because it may clog the recharge

structure. "first one or two shower should be flushed out through rain separator to avoid

contamination. This is very important, and all care should be taken to ensure that this has beendone."



Recharge Pits:-

Recharge pits are small pits of any shape rectangular, square or circular, contracted with brick or

stone masonry wall with weep hole at regular intervals. to of pit can be covered with perforated

covers. Bottom of pit should be filled with filter media.

The capacity of the pit can be designed on the basis of catchment area, rainfall intensity and

recharge rate of soil. Usually the dimensions of the pit may be of 1 to 2 m width and 2 to 3 m

deep depending on the depth of pervious strata. These pits are suitable for recharging of shallow

aquifers, and small houses.

Soak away or Recharge Shafts:-

Soak away or recharge shafts are provided where upper layer of soil is alluvial or less pervious.These are bored hole of 30 cm dia. up to 10 to 15 m deep, depending on depth of pervious layer.

Bore should be lined with slotted/perforated PVC/MS pipe to prevent collapse of the vertical

sides. At the top of soak away required size sump is constructed to retain runoff before the filters

through soak away. Sump should be filled with filter media.



Recharging of dug wells:-

Dug well can be used as recharge structure. Rainwater from the rooftop is diverted to dug wells

after passing it through filtration bed. Cleaning and desalting of dug well should be done

regularly to enhance the recharge rate. The filtration method suggested for bore well recharging

could be used.



Recharge Trenches:-

Recharge trench in provided where upper impervious layer of soil is shallow. It is a trench

excavated on the ground and refilled with porous media like pebbles, boulder or brickbats. it is

usually made for harvesting the surface runoff. Bore wells can also be provided inside the trench

as recharge shafts to enhance percolation. The length of the trench is decided as per the amount

of runoff expected. This method is suitable for small houses, playgrounds, parks and roadside

drains. The recharge trench can be of size 0.50 to 1.0 m wide and 1.0 to 1.5 m deep.

Percolation tanks

Percolation tanks are artificially created surface water bodies, submerging a land area with

adequate permeability to facilitate sufficient percolation to recharge the ground water. These can

be built in big campuses where land is available and topography is suitable.

Surface run-off and roof top water can be diverted to this tank. Water accumulating in the tank

percolates in the solid to augment the ground water. The stored water can be used directly for

gardening and raw use. Percolation tanks should be built in gardens, open spaces and roadside

green belts of urban area.



Conclusion:-

Rainwater harvesting is an important new technique to confront the increase in shortage of water

and to manage the water judiciously. However a systematic and structural procedural approachis required to ensure that the maximum benefit is drawn from this technique. Great care is also

required to ensure that negative externalities are not generated by the adoption of this technique

such as pollution of ground water or flooding damage to structures, or weakening of foundations

etc.



REFERENCES:-

Google.in

wikipedia

roof top rainwater harvesting

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