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Hi All,
First, thanks to the forum and all the forum members. This forum has lot of information for beginners. I started with zero knowledge about house construction and I learnt lot of things by going through this website.

From past few days I am trying to understand about Rain water harvesting and also went through couple of threads in this fourm. I have couple questions. Please help me

I will be constructing house on 30x45 site at Bangalore north. Currently there is no Cauvery water available to our layout and chances of getting borewell water is also less, so thinking of going for RWH.

1. Bangalore has average rain fall of around 1000mm and so thinking to have bigger sump for rain water storage. My plan is to go for 30,000L (30K) sump for rain water and one more sump of 7000L for future cauvery water/tanker water. Are these sizes practical ? What should be the ideal size for storing rain water in Bangalore ?

2. There is a mixed opinion on using rain water for drinking purpose. Can I use it for drinking ? Plan is to use both sumps initially for rain water storage and use it for everything.

3. Since there are two sumps should I go for two water pumps or any other alternative ideas to save cost

4. I am planning to keep lot of pots for organic terrace gardening(not lawn). Is it a good idea to collect water from entire terrace or should I have a separate terrace space reserved for rain water catchment? If I exclude garden space then I think I will have less space to collect rain water. Any ideas or alternative thoughts will be helpful

5. Brick vs concrete sump. Which is suitable ?

Thanks in advance.
PKumar

Unless you have a elaborate in house water treatment system with Sand and Activated Carbon filters and RO , No matter how clean you keep your terrace and regularly clean it.
a) Rain water collected on terrace may have loads of Bee's Excreta( which contain micro spores\ pollen and potential allergens),
b) excreta of Crows , Bats and other flying insects and birds. These can contain harmful viruses and bacteria and inorganic dissolvable compounds.
c) Dust in form of accumulated film over large area of terrace, nano sized Carbon particles, and microfine silica and other man made solid air pollutants and potent carcinogens.
d)if you have organic garden in pots, the dripping water from pots can contain leached salts and other organic acids.

I say let nature treat the rain and recharge its aquifers.

1) How many days you will get rain and periodicity in a year is more important than the ""avg mm"" rain. Typically it rains few days in a week continuously and such events may happen 4 or 5 times during a rainy season spanning 2 or 3 months. rest of rainy season is mostly thunderclouds , gloomy weather and drizzle.
30kl is too big a tank , 10kl would be still on the higher side for RW storage.

2) Any day concrete sump is robust, repairable and less prone to damage and fractures, but might cost you 2.5x to 3x of the brick one. it can easily be in range of 3 to 4 lakhs.

kumar

Rain water can be used for all purpose. there is no harm.
I suggest you meet this amazing person Mr. Shivakumar. This great person is living only with Rain water from last 20 years in Bangalore.
He doesn't have BWSSB connection at all neither for Kaveri Water nor sanitary connection. You get answers for all your queries.

http://kscst.org.in/rwh_files/rwh_sourabha.html

Thanks msn1270. Actually, Mr. Shivakumar is the one who motivated me. I will try to contact him.

Thanks Nivas. Your points made me to research again on these aspects. Regarding cost I think 3-4L is too costly.

Any thoughts on what is the suggested sump size for RWH considering Bangalore rain ? Mine is 30x45 site and going for G+2 floors.