The answer is about 623 gallons.
Gallons of water per square foot of roof.
If your average rainfall was 25 inches year your annual collection potential is 1 120 x 25 28 000 gallons year.
To calculate the runoff from any given rainfall.
Up to 6 12 7 12 8 12.
Take a guess what is the volume of water that runs off a 1 000 square foot roof during a 1 rain storm.
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.
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.
Calculate rainwater collection in gallons rain fall inches.
For example on a 2 000 square foot roof you can collect 2 000 x 0 56 1 120 gallons inch of rain.
It doesn t take many sticks leaves or needles to impede the proper flow of.
For example a 3 inch per hour rainfall will build up to a 3 inch depth on a flat roof in one hour at the rate of 1 87 gallons per hour sq.
The collectable rainwater from the roof can be calculated in gallons using this calculator based on the rainfall and area.
Using a 10 000 sq.
To figure out the square footage of a surface multiply the width x length.
Or 0312 gallons per minute sq.
Roof area square feet per linear ft of gutter underneath.
The square footage of a roof is the same whether it is pitched or flat.
Multiply the cubic feet by the amount of water per cubic foot which is 7 48 gallons.
Take the dimensions of the footprint of your roof and convert them to inches.
So a 50 x 20 roof is 600 x 240 multiply the roof dimensions by the number of inches of rainfall.
Meaning you can capture about 62 gallons per sq ft.