Rain water harvesting


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Every drop of water is precious.

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Rain water harvesting

  1. 1. RooftopRainwaterHarvestingPre-implementationguide for schoolsNitin ChhaperwalClass :- ixRoll No. :- 915Prepared By ;-
  2. 2. Why?At the city level• Reduces water demand• Reduces energy demand – lesser energy required for water distribution• Improves groundwater situation• In coastal areas, it can counter saline water intrusion into freshwater aquifers• Prevents urban flooding
  3. 3. Why?At the school level• Reduces water bills• Sets an example for students and parents• Improves groundwater table if rainwater is recharged• Improves groundwater quality by dilution(rainwater has nearly neutral pH and zero hardness)
  4. 4. How?Recharge if there’s excessThe concept is simpleCollectStoreUse
  5. 5. ROOFTOP RAINWATER HARVESTINGCatchment – rooftopTransportation – Down take pipesFilters – First flush deviceLeaf and grit filterStorage – Tank / wellComponents
  6. 6. How much water can we harvest?Rain Water CollectedFrom Both Sides of theRoofWRain WaterCollected From oneSide of the RoofAmount of rainfall(mm)x =WCatchment Area(m2)Volume of water received(Litres)
  7. 7. The water that leaves the rooftop may be 65 – 90% ofthe water that falls on itRoof material absorbs some waterMore water loss if roof is flatEvaporation losses
  8. 8. Keep the roof clean• Remove leaves, plant debris,bird and animal droppings, deadrodents or birds• No tar / bitumen on the roof• No chemical pesticides orfertilizers for rooftop garden
  9. 9. TransportationPipe size is calculated based on peak flow rates(rooftop area and peak rainfall rate)Gutter (open on top)Downtake pipe (cylindrical)PVC pipes preferred. Do not use lead pipes
  10. 10. Take care….• Clamp gutters and down take pipes well• Keep gutters clean of leaves• See that leaves do not clog a down take pipe(Jaali or leaf filter may be needed at rooftop discharge pointbut this may also be a problem if leaf debris collects on itand water stagnates on the roof)• Gutters and down take pipes should be gently slopingtowards the storage tank, so that there is no stagnation ofwater in the pipe
  11. 11. Filtershttp://www.rainyfilters.com/rainwater.aspxGravelSandInletOut flowOver flowGravelRecharge tankFilterStorage tankDown take pipesFirst flushCheck and clean filters before and after each rainy seasonMake your own filter with sand,charcoal and gravelOrBuy a filter off the shelf
  12. 12. First flush• The first rain carries with it a lot of filth fromthe rooftop and dissolved air pollutants• This rainwater should be diverted away fromthe storage tank using a first flush device.• Some filters have a first flush systemintegrated in them• Check and clean first flush devicesregularly.First flush standpipe
  13. 13. STORAGE SIZEDepends on• Rainwater availability• Water requirement• Budget (storage tank is most expensive part of (rwh system)• Available space and aestheticsExcess water can be diverted into a groundwater recharge systemDo a wateraudit to checkwaterrequirement.
  14. 14. STORAGE• Above ground– Ground level or Intermediate floor level– Just below roof• Below groundSave on pumping cost
  15. 15. Storage tank features• Durable and no leaks• Built on a strong and stable substrate that can support the tank filled with water• Opaque – presence of light can cause algal growth in tank• Secure and impervious cover• Vents to be covered with insect proof mesh• Located as close as possible to demand and supply points to reduce plumbing
  16. 16. • Overflow pipe should be provided close to the top, to reduce dead space.• Overflow pipe diameter should be equal to inlet pipe diameter• Overflow pipe should lead excess water away from the foundation of tank and other buildings.Preferably the overflow should be led into a groundwater recharge system or a garden• There will be sedimentation in the tank. Taps and pipes to draw water from the tank shouldnot be very close to the bottom to prevent sediments from entering the plumbing systemand clogging it.Storage tank features
  17. 17. What can we use the rain water for?If used for drinking, it is absolutely necessary tocheck water quality in a lab and treat as required
  18. 18. Other factors• Some changes may be required inplumbing, if retrofit• Clean rwh system regularly– Rooftop everyday– Tank after a rainy season– Filter after a rainy season
  19. 19. RainwaterHarvestingDOITNOW!