Reply With Quote36" is around 900mm of rain, this means in that year each m2 will catch 900mm deep of water which is 900L. 900*70=63000l/ year potential.
Rain water collection area formulae
I have just had the old shed roof repaired after it was damaged last November and now its one slope 7 metres wide by 10 metres long giving an area of 70 square metres.
The guttering has yet to be done and its planned to drain the roof into tank(s) for non domestic use but I am curious as to how much water a roof of this size could collect given a known fall of rain.
I am sure I have seen a formulae applied to houses that have no Town Water supply to determine what collection area is needed to fill the required sized tanks.
I am guessing this formulea would be based on the mean average rainfall which means one year you get nothing to a deluge the next.
The average rainfall here was around 36 inches a year but mostly in the form of light misty drizzle with the occasional Gully Washers but with the non existent Global Warming it dropped to around 15 inches for several years and although we got 3 years rain in as many months, we're back to less than 24 inches on average.
Any details would be appreciated.
I stand unequivicably behind everything I say, I just dont ever remember saying it !!
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36" is around 900mm of rain, this means in that year each m2 will catch 900mm deep of water which is 900L. 900*70=63000l/ year potential.
Thanks crazy,
Sorry I forgot to convert to metric but thats an appreciable amount of water, IF it rains.
So its the rainfall in mm over a M2 = volume collected.
I was thinking if it was viable to collect that rainwater and I could use it to flush the Loo and save that cost on the water rates but if the water is collected and basically filtered, it could also be used in the washing machine, food for thought.
I stand unequivicably behind everything I say
We're mixing Metric with Inches ???
It then follows that 36 inches equals 0.9 Meters. Over 702 Meters, that's 630 Liters.Originally Posted by gordon_s1942
Also that 24 inches equals 0.61 Meters. Over 702 Meters, that's 427 Liters.
Rainwater has been drunk for centuries with little effect upon the human populace, in a city, with the pollution as stuff, it might be a little more toxic, now. FWIW, I try and use only rainwater for everything at home, drinking, cooking, cleaning, even flushing. Yes, I do have a couple of good sized tanks, and I do run out occasionally (I have the facility to switch back to town water if necessary)
I don't have mains water available and have never had a problem drinking harvested water (18 years now)
Water volume (Litres) = average annual rainfall (millimetre)
x coefficient of runoff x roof area (metres2)
A coefficient of runoff of 0.9 can be used to obtain a rough estimate.
eg: 100 m2 x 550 mm rainfall x 0.9 = 49,500 litres.
Last edited by freakee1; 12-10-13 at 01:26 AM.
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Not to be a nit-picker but I see a considerable underestimation there.It then follows that 36 inches equals 0.9 Meters. Over 702 Meters, that's 630 Liters.
Also that 24 inches equals 0.61 Meters. Over 702 Meters, that's 427 Liters.
IE 0.9m over 70 square metres = 63 cubic metres and at 1000 litres/m^3, 63000 litres would be the theoretical maximum yield.
beer4life (29-10-13)
Yes, you are correct.
I got caught in the middle of Forum updating. I did correct it, however that did not stick. By the time I found that, too late to edit again.
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