Rainwater can be collected from the roofs using the rain water harvesting method.
Gallons of water on roof.
Converting this to gallons per minute per square foot gpm ft 2.
How much will your roof be able to capture.
To calculate the runoff from any given rainfall.
Required roof drainage flow rate in gallons per minute 0 0104 x rainfall rate x roof area where rainfall rate is expressed in inches per hour and roof area is given in square feet.
This means that each square foot captures about 62 gallons per inch of rain.
The answer is about 623 gallons.
So a 50 x 20 roof is 600 x 240 multiply the roof dimensions by the number of inches of rainfall.
To find how much rain you can collect in an average rain year multiply this number by the average inches of rain.
If your average rainfall was 25 inches year your annual collection potential is 1 120 x 25 28 000 gallons year.
Rainwater collection calculator in gallons.
For example on a 2 000 square foot roof you can collect 2 000 x 0 56 1 120 gallons inch of rain.
The collectable rainwater from the roof can be calculated in gallons using this calculator based on the rainfall and area.
To a depth of 1 in 1 hour.
Roof area m2 x precipitation amount mm amount collected liters.
Simply take your roof s square footage and multiply by 62.
Roof area ft2 x precipitation amount in x 0 623 amount collected gallons easy formula to remember.
1 inch of rainfall in an hour will cover 1 sq ft.
Rainwater collection calculation formulas and equations.
1 of rain on 1 000 sf roof will yield 623 gallons.