How Much Rainwater Will My Roof Collect

One inch of rain falling on 1000 sq ft of roof will deposit 623 gallons of water.

How much rainwater will my roof collect.

This capacity can be calculated using the following formula. If your average rainfall was 25 inches year your annual collection potential is 1 120 x 25 28 000 gallons year. That is the theoretical best case outcome for this scenario. So each inch of rain on your roof will have 763 gallons of water going down your downspouts.

1 of rain x 1 sq. To find how much rain you can collect in an average rain year multiply this number by the average inches of rain. To get an idea how much water the roof of your own house might yield use the rainfall harvest calculator above. 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. 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. So 70 80 1400 means you have 1225 net sq ft of collection area. 1 of rain on 1 000 sf roof will yield 623 gallons.

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. Concrete tile may leave you with alkalinity in your water but this isn t necessarily a problem. For example on a 2 000 square foot roof you can collect 2 000 x 0 56 1 120 gallons inch of rain.

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. 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. Keep in mind most rain falls over 2 3 months of a year.

Rainwater collection calculation formulas and equations. When you look at the numbers it s surprising how much water you can collect every time it rains. Even during a drought you should easily be able to collect 70 000 to 80 000 gallons of water with a proper. 0 623 gallons easy to remember formula.

You can use the precipitation map below to find an approximate amount for your area. Roof area m2 x precipitation amount mm amount collected liters. Amount of water since los angeles is commonly plagued by drought you may be wondering if collecting rainwater is useful.