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
- 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.