Design Tips

Some of the important design tips would be as follows:

Design your roof well for rainwater collection

  • a flat roof can be gently sloped to drain water towards the storage system. A 'nahani trap' or 'floor trap' can be placed at the time of casting the roof just near the inlets of the down water pipes
  • sloping roofs should have a gutter of PVC or zinc sheet to collect water & channel it to the down water pipe system.
  • roofs should be uncluttered & should be easy to clean by sweeping & swabbing if necessary.

Down water pipes should be designed well

  • 90mm dia. PVC pipes resistant to UV rays appear to be the best bet as downwater pipes. Of course, this depends upon the roof area to be drained.
  • 3 to 4 downwater pipes seem sufficient for 1000 to 1200 sft area

Filter the rainwater before storage

  • filtering can be as basic as a floor trap placed before the water enters the downwater pipe or a piece of sponge placed at the inlet of the downwater pipe
  • a PVC bucket with gravel, sand & charcoal is a good filter before rainwater is stored
  • a PVC drum with sponge at the inlet & outlet is also a filter
  • a small two chamber inspection/ filter tank can also be devised

Try to determine your storage system at the planning stage itself.

Would it be a:

  • roof level storage tank
  • ground level drum or masonry tank
  • below the ground sump
  • partially below ground and partially above ground tank

Locate the storage system properly

  • Roof level storage tanks may need to be at the rear of the house or on the sides so that it is neither obtrusive nor visually offensive.
  • Ground level drums or tanks occupy space and should not hinder movement or appear unsightly.
  • Below the ground sump is a good option since most new constructions in Bangalore go in for sumps anyway. Sumps are hidden from view, less costly to build and do not obstruct movement.
    Note: always provide for an outlet for excess collection of water from the storage system

Further treatment of excess rainwater

  • It is a common perception that water stored for long goes bad. If water does not contain any organic material and if it is stored in a clean container it can stay for a long time.
  • Some small treatment like ‘alum dosing’ or ‘chlorination’can also be done to stored water to improve its quality.
  • Addition of a small quantity of alum dissolved in half a bucket of water will bring down the suspended solids and clear the stored rainwater.
  • Similarly adding a small quantity of bleached powder to half a bucket of water and then mixing it with the stored rainwater will kill bacterial contamination.
  • Great care should be excercised while chlorinating and it is not particularly recommended.
  • It is always recommended that water used for drinking should be boiled and filtered invariably.
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