How Much Rainwater Will My Roof Collect

1 of rain on 1 000 sf roof will yield 623 gallons.

How much rainwater will my roof collect. Keep in mind most rain falls over 2 3 months of a year. To get an idea how much water the roof of your own house might yield use the rainfall harvest calculator above. Roof area ft2 x precipitation amount in x 0 623 amount collected gallons easy formula to remember. For example on a 2 000 square foot roof you can collect 2 000 x 0 56 1 120 gallons inch of rain.

If you have 1 000 square feet of roof on your house and it rains just 1 inch you can collect 600 gallons of water to be used in your garden for washing your car or just for drop irrigation around your property. With over 600 gallons of high quality water available from a single inch of rain falling on 1000 square foot surface even an 85 collection efficiency estimated for clay tile will give you a lot of high quality water. If your average rainfall was 25 inches year your annual collection potential is 1 120 x 25 28 000 gallons year. 1 of rainfall over 1 000 sf will yield 623 gallons to calculate the amount of rainwater you can collect you need to know your annual average precipitation for your area.

That s 600 less gallons you have to pay for and use from your town water supply. Roughly speaking 1 millimetre of rain over 1 square metre of roof equals 1 litre of water. So 70 80 1400 means you have 1225 net sq ft of collection area. That is the theoretical best case outcome for this scenario.

When you look at the numbers it s surprising how much water you can collect every time it rains. It isn t uncommon for an area to collect up to 350mm of rain in just one month even in rural areas. So each inch of rain on your roof will have 763 gallons of water going down your downspouts. One inch of rain falling on 1000 sq ft of roof will deposit 623 gallons of water.

0 623 gallons easy to remember formula. Just a half inch of rain falling on a 1 000 square foot roof will yield 300 gallons of water. This capacity can be calculated using the following formula. Roof area m2 x precipitation amount mm amount collected liters.

Even during a drought you should easily be able to collect 70 000 to 80 000 gallons of water with a proper. Rainwater collection calculation formulas and equations. You can use the precipitation map below to find an approximate amount for your area. Concrete tile may leave you with alkalinity in your water but this isn t necessarily a problem.

To find how much rain you can collect in an average rain year multiply this number by the average inches of rain. 1 of rain x 1 sq. An average suburban roof of 200m 2 with such a rain fall can potentially harvest 100 000l of rainwater 200m 2 500mm 100 000l.