How Much Rain Water Will My Roof Collect

For example on a 2 000 square foot roof you can collect 2 000 x 0 56 1 120 gallons inch of rain.

How much rain water will my roof collect.

Keep in mind most rain falls over 2 3 months of a year. Annual rainfall in millimetres x roof surface area in square metres roof catchment capacity. Just a half inch of rain falling on a 1 000 square foot roof will yield 300 gallons of water. It isn t uncommon for an area to collect up to 350mm of rain in just one month even in rural areas.

An average suburban roof of 200m 2 with such a rain fall can potentially harvest 100 000l of rainwater 200m 2 500mm 100 000l. Rainwater collection calculation formulas and equations roof area ft2 x precipitation amount in x 0 623 amount collected gallons easy formula to remember. When you look at the numbers it s surprising how much water you can collect every time it rains. John hickenlooper recently signed house bill 1005 which allows a maximum of two rain barrels with a combined capacity of 110 gallons are allowed at each household.

With two inches of rain you can collect around 1 240 gallons. This capacity can be calculated using the following formula. Roughly speaking 1 millimetre of rain over 1 square metre of roof equals 1 litre of water. Concrete tile may leave you with alkalinity in your water but this isn t necessarily a problem.

So how can you do the math for your own roof. 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. To get an idea how much water the roof of your own house might yield use the rainfall harvest calculator above.

To find how much rain you can collect in an average rain year multiply this number by the average inches 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. Now most homeowners in the state are allowed to collect precipitation for later outdoor use. 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.

1 of rain on 1 000 sf roof will yield 623 gallons roof area m2 x precipitation amount mm amount collected liters. The measure is to take effect on aug. 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. If your average rainfall was 25 inches year your annual collection potential is 1 120 x 25 28 000 gallons year.

You can use the precipitation map below to find an approximate amount for your area.