Designing the Rainwater Collection Tank
Equation V = A2 x i x c x 7.5 gals./ ft.3 where:
V= volume of rain water collection tank (gallons)
A2= surface area roof (square feet)
i= rainfall (1″=.08 ft.) [example]
c= coefficient of runoff (.9 for impervious areas)
7.5= conversion factor (gallons per cubic foot)
calculation example
600 gallons = 1000 ft.2 x 0.08 ft. x 0.90 x 7.5 gallons/ft.3
