How Much Rainwater Will My Roof Collect

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.

How much rainwater will my roof collect.

0 623 gallons easy to remember formula. Keep in mind most rain falls over 2 3 months of a year. Roof area m2 x precipitation amount mm amount collected liters. For example on a 2 000 square foot roof you can collect 2 000 x 0 56 1 120 gallons inch of rain.

That s 600 less gallons you have to pay for and use from your town water supply. Amount of water since los angeles is commonly plagued by drought you may be wondering if collecting rainwater is useful. 1 of rain on 1 000 sf roof will yield 623 gallons. Roof area ft2 x precipitation amount in x 0 623 amount collected gallons easy formula to remember.

This capacity can be calculated using the following formula. One inch of rain falling on 1000 sq ft of roof will deposit 623 gallons of water. If your average rainfall was 25 inches year your annual collection potential is 1 120 x 25 28 000 gallons year. Concrete tile may leave you with alkalinity in your water but this isn t necessarily a problem.

So 70 80 1400 means you have 1225 net sq ft of collection area. It isn t uncommon for an area to collect up to 350mm of rain in just one month even in rural areas. 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.

Most cisterns and full rainwater collection kits can collect several hundred gallons of water or more at a time. An average suburban roof of 200m 2 with such a rain fall can potentially harvest 100 000l of rainwater 200m 2 500mm 100 000l. To get an idea how much water the roof of your own house might yield use the rainfall harvest calculator above. So each inch of rain on your roof will have 763 gallons of water going down your downspouts.

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 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. 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.

That is the theoretical best case outcome for this scenario. Rainwater collection calculation formulas and equations. Just a half inch of rain falling on a 1 000 square foot roof will yield 300 gallons of water.