12-08-2012, 04:45 AM
A square foot of horizontal surface receives approximately
0.625 gallons of water with each inch of rainfall.
(6) Surfaces that slope, like your roof, catch less water
per square foot of surface area. So it is not the area of
roof surface that you need to measure, but the roof’s
“footprint,” the area of ground under it.
This is quoted from Trish's book from UH about rainwater harvesting. So an inch of rain on 2000 sq. ft. is 1250 gallons. We divert about half of our rainwater past the tank here in Leilani and for two of us have never had less than a half tank. Similar to PV you buy low-flow appliances to conserve what you get and the less annual rainfall you have the larger collection and storage you need.
Air in the top of the tank is much warmer than the water usually so run your hand up the side and you should be able to tell what the water level is.
Jay
0.625 gallons of water with each inch of rainfall.
(6) Surfaces that slope, like your roof, catch less water
per square foot of surface area. So it is not the area of
roof surface that you need to measure, but the roof’s
“footprint,” the area of ground under it.
This is quoted from Trish's book from UH about rainwater harvesting. So an inch of rain on 2000 sq. ft. is 1250 gallons. We divert about half of our rainwater past the tank here in Leilani and for two of us have never had less than a half tank. Similar to PV you buy low-flow appliances to conserve what you get and the less annual rainfall you have the larger collection and storage you need.
Air in the top of the tank is much warmer than the water usually so run your hand up the side and you should be able to tell what the water level is.
Jay
Jay