Valley, AL rainwater: 41,759 gallons off a roof

Rainwater from a roof in Valley, AL

41,759gallons a year

That is a 1,500 sq ft asphalt roof under Valley, AL's normal 52.5 inches of rain, about 795 gallons for every inch that falls.

In Valley, AL a single barrel does most of the work. Storms come often enough that a small tank refills before it runs dry, and a bigger one would mostly sit full.

Rainfall: NOAA 1991-2020 climate normals, the W Pt station (5.3 mi away). Valley, AL ranks 63rd wettest of the 66 cities covered in Alabama.

Month by month in Valley

Month	Rain (in)	Off the roof (gal)	Garden shortfall (gal)
Jan	4.88	3,879
Feb	4.71	3,744
Mar	5.31	4,220
Apr	4.59	3,648
May	3.89	3,092	57
Jun	3.90	3,100	56
Jul	4.70	3,736
Aug	3.98	3,163	46
Sep	3.67	2,917	85
Oct	3.12	2,480	153
Nov	4.37	3,473
Dec	5.42	4,308

Dec is the wettest month (5.42 in, 4,308 gal off the roof); Oct the driest (3.12 in). Garden shortfall is what a 200 sq ft vegetable bed needs beyond the rain that lands on it, April to October.

Barrel or cistern in Valley?

Best fit: one 55-gallon barrel, which delivers about 331 gallons to the garden in a normal year (83.2% of its need).

Before you buy, a 55-gallon barrel with a downspout diverter is the whole job. Check that the overflow points away from your foundation, because most of Valley's roof water will pass straight through it.

Tank	Water used (gal/yr)	Spills over (gal/yr)
55 gal	331	40,348
110 gal	331	40,348
165 gal	331	40,348
275 gal	331	40,348
550 gal	331	40,348
1,000 gal	331	40,348
1,500 gal	331	40,348
2,500 gal	331	40,348
5,000 gal	331	40,348

Simulated storm by storm through a normal year using the station's count of days with 0.1 in or more of rain each month.

Is rainwater collection legal in Alabama?

No rainwater harvesting regulations

From the 2015 (Pacific Northwest National Laboratory report 24347); not yet re-checked against current law, so check with your state water agency before building anything large. Source