### rainwater formula

Apr. 2nd, 2009 11:58 pm**gailmom.livejournal.com**

Just a quick post so I'll have this here for later, since one of our goals is to harvest rainwater.

F=footprint of roof (which is equal to square feet of ground covered)

R= average rainfall per year, in inches

to convert cubic feet to gallons, multiply by 7.5

So, according to

7.5(FR/12)=gallons per year of water that your roof can catch.

According to this site, our area gets 40 inches of rain per year. (srsly? ok). Let's say my roof covers 1800 sq ft (which isn't actually accurate, since that is the square footage of our home's living space, and we also have guttered roof over the garage, but close enough for now)...

Therefore 7.5[ (1800X40)/12]= (where the heck is my calculator....brb)

ok, here it is.

Holy @(%^#@%(@*#&$

*ahem*

So that would be roughly

F=footprint of roof (which is equal to square feet of ground covered)

R= average rainfall per year, in inches

to convert cubic feet to gallons, multiply by 7.5

So, according to

*food not lawns*by H.C. Flores, who apparently got this formula from Toby Hemenway who wrote*Gaia's Garden*(I note this because the formula doesn't actually make sense to me, so I can't confirm it's right):7.5(FR/12)=gallons per year of water that your roof can catch.

According to this site, our area gets 40 inches of rain per year. (srsly? ok). Let's say my roof covers 1800 sq ft (which isn't actually accurate, since that is the square footage of our home's living space, and we also have guttered roof over the garage, but close enough for now)...

Therefore 7.5[ (1800X40)/12]= (where the heck is my calculator....brb)

ok, here it is.

Holy @(%^#@%(@*#&$

*ahem*

So that would be roughly

**45,000 gallons**of rainwater we are currently not doing anything with.....huh. Yeah, I'd say it would be worthwhile to put rainbarrels on our list of "good stuff to save for sooner rather than later". Yup. yes. absolutely. wow.