How Much Rain Runs Off A Roof

For example if you have a roof that measures 50 square metres that equals 500 000 square cm 1 square metre 10 000 square cm.

How much rain runs off a roof.

However calctool s unit menus remove this issue doing all the unit conversion for you. So if you have 2 500 square feet of roof available for water catchment and a single inch of rain falls one day we see that. For example on a 2 000 square foot roof you can collect 2 000 x 0 56 1 120 gallons inch of rain. Keep in mind most rain falls over 2 3 months of a year.

Show comments you may like. Measure along the length of the house or building and along the width of the house or building in feet. You may be as astonished as we were to learn how much water runs off a roof in a rain storm. Take a guess what is the volume of water that runs off a 1 000 square foot roof during a 1 rain storm.

Multiply this by the rainfall to get the volume of rain. An average suburban roof of 200m 2 with such a rain fall can potentially harvest 100 000l of rainwater 200m 2 500mm 100 000l. How much rain water runs off your roof. If your average rainfall was 25 inches year your annual collection potential is 1 120 x 25 28 000 gallons year.

Here you can easily find how much rainwater you can collect from you roof how much you need to remove from a courtyard or how much runoff you can expect from an area of land. It isn t uncommon for an area to collect up to 350mm of rain in just one month even in rural areas. The answer is about 623 gallons. Assuming 5 cm of rain per hour.

The basic calculation is a x r 231 g where a is the area of your roof in square feet r is the amount of rain in inches and g is the amount of runoff in gallons. Step 1 determine the footprint of your structure f in square feet. Count the number of downspouts coming from your roof. While this is a normal aspect of roofing and gutters water that pours off of a roof and drenches an area like a door stoop or porch not only makes these spots slippery but water falling.

Although this calculation is simple in principle the units can make it a headache. 500 000 square cm multiplied by 5 cm is 2 500 000 cubic cm of rain. Multiply the two figures together to obtain the square footage of your roof step 2 determine the percentage of water collected from each downspout p.