How Much Rainwater Will My Roof Collect

Roughly speaking 1 millimetre of rain over 1 square metre of roof equals 1 litre of water.

How much rainwater will my roof collect.

So each inch of rain on your roof will have 763 gallons of water going down your downspouts. Roof area m2 x precipitation amount mm amount collected liters. An average suburban roof of 200m 2 with such a rain fall can potentially harvest 100 000l of rainwater 200m 2 500mm 100 000l. When you look at the numbers it s surprising how much water you can collect every time it rains.

This capacity can be calculated using the following formula. Roof area ft2 x precipitation amount in x 0 623 amount collected gallons easy formula to remember. 1 of rain on 1 000 sf roof will yield 623 gallons. Concrete tile may leave you with alkalinity in your water but this isn t necessarily a problem.

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. Most cisterns and full rainwater collection kits can collect several hundred gallons of water or more at a time. 1 of rain x 1 sq. For example on a 2 000 square foot roof you can collect 2 000 x 0 56 1 120 gallons inch 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. Keep in mind most rain falls over 2 3 months of a year. Even during a drought you should easily be able to collect 70 000 to 80 000 gallons of water with a proper.

One inch of rain falling on 1000 sq ft of roof will deposit 623 gallons of water. Just a half inch of rain falling on a 1 000 square foot roof will yield 300 gallons of water. Amount of water since los angeles is commonly plagued by drought you may be wondering if collecting rainwater is useful. You can use the precipitation map below to find an approximate amount for your area.

To find how much rain you can collect in an average rain year multiply this number by the average inches of rain. It isn t uncommon for an area to collect up to 350mm of rain in just one month even in rural areas. Rainwater collection calculation formulas and equations. 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. 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. That is the theoretical best case outcome for this scenario.