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RAIN WATER HARVESTING FROM ROOF TOPS USING FERRO CEMENT TANKS

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The system of harvesting water from rooftops is useful mainly for drinking water purposes. In this system rain water falling on the roofs can be collected through a system of pipes and semi circular channel of galvanized iron or PVC and is stored in tanks in a suitably sized storage tank for providing sufficient water for reasonably long duration. On the rooftop, as well as at the entry to the tanks simple filters are placed to remove dust and other particles. A simple diversion system is provided to keep out dirt from season's first rain, or rain after a long gap, which may bring along accumulated dirt from the roof. The package of Rainwater harvesting provides a system of pipes for collecting rainwater from roofs and a 3000 liters Ferro Cement Tank for each household. The choice of Ferro cement for tank construction is guided by consideration of optimizing cost and performance characteristics. If cheaper options with equal strength and longevity are available elsewhere these can be adopted after due consultation with the beneficiaries. Needless to say if the present capacity of the tank is found inadequate and necessity for larger capacity tank is subsequently felt for the villagers who find the technology suitable, another storage tank of similar or slightly larger capacity (5000 Ltr.) can be provided.

Benefits:
Rainwater harvesting from rooftops has several advantages as follows: -
* Drudgery and time spent by people, especially women, in fetching water from distant sources can be eliminated or considerably reduced.
* Rainwater being contamination free is safe for drinking and can thus minimize health risk from water borne diseases.
* Stored rainwater can also be used for drinking by animals and for other domestic purposes.
* It is a simple and cost effective collection of rainwater through ferro cement technology.
* Skill relating to Ferro cement technology can easily be passed on to local masons who can use their skill profitably in other ferro cement based products.

Conditions for Adoption:
* Rainwater harvesting from rooftops is most suited in the areas of severe water scarcity. e.g., absence of potable water source in the village, nearest water source being far away or drudgery involved in bringing water in hilly areas or other difficult terrains.
* Adequate rainfall should be available in the area.
* The roof should preferably be tile, RCC, RBC, GI etc., preferably with a slight slope: thatched roof would pose problems of dirt and other contamination.

Operational Precautions:
In order to have potable drinking water, following precautions should be taken:
* Smooth roof surface is desirable for easy flow of water.
* The roof should not be under trees to prevent dirty leaves and bird droppings falling on it.
* The ferro cement tank should be properly sealed to keep out mosquitoes, insects, lizards etc.
* Before the onset of monsoon or after one or two rains, the roofs should be properly cleaned and the water should be diverted away from the storage tank to ensure collection of clean water only.
* Filters should be cleaned periodically to remove impurities and dirt.
* The ferro cement tank should be periodically cleaned at least before the start of each rainy season.
* All joints should be regularly checked for leakage and repaired wherever necessary.

Material required:
A tabular statement describing material required for constructing one rain water harvesting system of 3,000 Litre capacity including collection system and ferro cement storage tank, along with the quantity of the materials with approximate cost is annexed. Construction Process: The process of construction of ferro cement tank is similar to fabrication of other products from ferro cement technologies. Special consideration needs to be taken for removing the connecting pipe or for otherwise diverting the rooftop water from storage tank so that dirt and other impurities from the roof are not allowed to enter the storage tanks. Cost estimate for Roof Top Rain Water Harvesting Tank ( 3000 litres capacity)
Note: 1. The maximum of 10% leverage can be given for projects to be initiated in difficult/un-reached/ hilly areas because of increase in costs towards cartage, material cost etc.
2. While strict insistence should be made upon on VO/beneficiary meeting the total labour cost, relaxation in this regard can be exercised from case to case basis in respect of projects initiated in these areas.