How Much Rain Collected From Roof

To find how much rain you can collect in an average rain year multiply this number by the average inches of rain.

How much rain collected from roof.

Just a half inch of rain falling on a 1 000 square foot roof will yield 300 gallons of water. To get an idea how much water the roof of your own house might yield use the rainfall harvest calculator above. When you look at the numbers it s surprising how much water you can collect every time it rains. Rainwater collection calculation formulas and equations roof area ft2 x precipitation amount in x 0 623 amount collected gallons easy formula to remember.

Gallons collected per inch of rainfall 0 62 total collecting area of roof in square feet so if you have a 1 000 square foot house you can potentially collect 0 62 1 000 620 gallons of water every time it rains an inch. So how can you do the math for your own roof. 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. It isn t uncommon for an area to collect up to 350mm of rain in just one month even in rural areas.

That s 600 less gallons you have to pay for and use from your town water supply. Rain barrel supplies list. If your average rainfall was 25 inches year your annual collection potential is 1 120 x 25 28 000 gallons year. Keep in mind most rain falls over 2 3 months of a year.

An average suburban roof of 200m 2 with such a rain fall can potentially harvest 100 000l of rainwater 200m 2 500mm 100 000l.