How Much Rainwater Does My Roof Collect

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

How much rainwater does my roof collect.

1 of rain x 1 sq. If you can try to use a billboard tarp which is around 20 in 30 in 51 cm 76 cm in size to collect as much rainwater as you can. 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.

To get an idea how much water the roof of your own house might yield use the rainfall harvest calculator above. Rain barrel supplies list. You can use the precipitation map below to find an approximate amount for your area. Roughly speaking 1 millimetre of rain over 1 square metre of roof equals 1 litre of water.

Keep in mind most rain falls over 2 3 months of a year. It isn t uncommon for an area to collect up to 350mm of rain in just one month even in rural areas. 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.

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. 0 623 gallons easy to remember formula. You can use a tarp of any size to collect rainwater but a larger the surface area the more water you ll harvest. For example on a 2 000 square foot roof you can collect 2 000 x 0 56 1 120 gallons inch of rain.

With two inches of rain you can collect around 1 240 gallons. 1 of rain on 1 000 sf roof will yield 623 gallons roof area m2 x precipitation amount mm amount collected liters other water conservation calculators. An average suburban roof of 200m 2 with such a rain fall can potentially harvest 100 000l of rainwater 200m 2 500mm 100 000l. Roof area ft2 x precipitation amount in x 0 623 amount collected gallons easy formula to remember.

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. When you look at the numbers it s surprising how much water you can collect every time it rains. That s 600 less gallons you have to pay for and use from your town water supply. Annual rainfall in millimetres x roof surface area in square metres roof catchment capacity.