Skip to Content


223 users have liked.
Everything elseWater

 This blog entry is to capture some RWH calculations and upload an excel file to show the calculations.

  1. five membered family - living in 60x 40 plot, having daily usage per member of 150 liters of water
  2. 100% coverage for RWH - tank of 15000 liters will be sufficient for 78% of water needs
  3. 80% coverage for RWH - tank of 5000 liters will be sufficient for 67% of water needs.

Please find attached excel sheet, those interested can vary the green cells to check out efficiencies and coverage.

rwh.xls67.5 KB


srkulhalli's picture

Wow ! Good start

154 users have liked.


The XLS is very good to do a first cut estimate. One minor comment - your F5 , G5... etc should have $C$6, instead of $C$5 to take into account where you dont utilise all the water falling on the site

One thing I observer is the granularity is a month. This might be OK in most cases, but if the storage is small, it may still miss out in situations where the rain might be lumped only into a few days on the month.

I found one more XLS from rainwaterclub.

Now if I put in the same data there as in your sheet, I find the numbers dont tally

216 sq m area, 750 litres per day - yours shows 75%

whereas the other one shows 151 days ~ 41%.

I think in this case they have looked at the daily spread and is probably more realistic, but the difference is huge. I havent really understood this XLS sheet though. 


silkboard's picture

Cost savings calculator?

122 users have liked.

Sweet - simple and easy to understand.

The sheet will be complete with some numbers on money front.

  • One time Investment required (aka Capital expenditure)
  • Maintenance costs
  • Money saved (taking current cost of water from BWSSB)

I know that cost is not the main incentive for citizens to 'upgrade' to RWH - after all, we pay peanuts for water - but when I ask the non-praja type people, there are cost perceptions around RWH. comment guidelines

Posting Guidelines apply for comments as well. No foul language, hate mongering or personal attacks. If criticizing third person or an authority, you must be fact based, as constructive as possible, and use gentle words. Avoid going off-topic no matter how nice your comment is. Moderators reserve the right to either edit or simply delete comments that don't meet these guidelines. If you are nice enough to realize you violated the guidelines, please save Moderators some time by editing and fixing yourself. Thanks!

about seo | blog