Calculating rainfall collection

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Byrned

453 posts

Ultimate Geek
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Topic # 25150 13-Aug-2008 14:29

A very off topic off topic!

I'm trying to work out what size water storage tank I will require for our house but I'm not sure if I've calculated it properly.

The surface area of the roof is approx. 90m2. and from what I can work out average rainfall per year 1150mm per year. From what I can work out that should equal about 103500L per year.

Is this correct? It seems like a lot!

Cheers

wellygary

3318 posts

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Reply # 156593 13-Aug-2008 14:49

Sounds roughly right 1150mm is close to 1m,* 90m2, = 90 Cubic Metres, = 90,000 litres, so you are in the right ball park,

Although you dont want to capture all of this, ideally you will have a diverter that dumps and offloads the first 50l of each rainstorm ( all the junk in the gutters and the bird crap off the roof).

Dratsab

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Reply # 156609 13-Aug-2008 15:39

There's a few other things to take into consideration:
- When does the rain usually fall (seasonality) and at what rates
- How much you might use over the different seasons (and thus how much you need to store

Obviously the 1.15m of rain isn't going to fall in one day, so you won't need a 103k litre tank...

The best advice for your area will come from people:
- With water tanks
- Who install water tanks

Good luck!