Here's What I Think
How should we conserve water?
I found the following figures for usage per day per person:
We probably use about 150-300 litres per day per person. With due care we could use roof water for all but drinking and cooking - but certainly to flush the loo.
Suppose we have a house in the city with a roof area of 100 m2 and a land area of 400 m2.
In Auckland we sometimes get as much as 25mm of rain in 24 hours and 1100 mm pa.
To capture this for the whole 400m2 we need a tank for 10,000 litres spare capacity. Some of this [say, a 1000 litre tank] could be at the roof level and so flush the loo - without an electric pump being used all the time.
Then in the winter keep the big tank near empty - say no more than 1/3rd full - use it to top-up the top tank - and absorb that downpour - then lower it by flushing it into the stormwater reticulation when it is no longer raining.
In summer use it to water the garden - but we must keep it no less than 1/3rd full - unless there is a drought!
Can all this be automated? Yes - and the equipment will not be much more than a single water bill.
Will this cost much? Not much - except for the big tank installation - but perhaps that can be subsidised by the local body - or only required for new buildings.
How much will this strategy reduce the costs of water and storm water reticulation in our cities?
2008 - Ian Mitchell
22A Goldie Street St Heliers, Auckland, Ph: 09 5851580