How Much Rain Runs Off A Roof

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

How much rain runs off a roof.

However calctool s unit menus remove this issue doing all the unit conversion for you. Although this calculation is simple in principle the units can make it a headache. 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.

500 000 square cm multiplied by 5 cm is 2 500 000 cubic cm of rain. 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. Just multiple the square footage of roof space you have available x 0 6 gallons per square foot per inch of rain and you can see how much water you can collect from each inch of rain that falls. Divide 100 by the number of downspouts in order to obtain the percentage of water collected from each downspout.

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. For example on a 2 000 square foot roof you can collect 2 000 x 0 56 1 120 gallons inch of rain. Measure along the length of the house or building and along the width of the house or building in feet. Show comments you may like.

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. Count the number of downspouts coming from your roof. An average suburban roof of 200m 2 with such a rain fall can potentially harvest 100 000l of rainwater 200m 2 500mm 100 000l. Multiply this by the rainfall to get the volume of rain.

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. Assuming 5 cm of rain per hour. 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.

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. Step 1 determine the footprint of your structure f in square feet. The answer is about 623 gallons.