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.