Rexburg, ID rainwater: 10,038 gallons off a roof

Rexburg, ID: gallons off the roof each year

10,038gallons a year

That is a 1,500 sq ft asphalt roof under Rexburg, ID's normal 12.6 inches of rain, about 795 gallons for every inch that falls.

Rexburg, ID has gaps between storms long enough to drain a single barrel. Around 165 gallons of storage catches most of what is worth catching.

Rainfall: NOAA 1991-2020 climate normals, the Rexburg Byu Idaho station (1.0 mi away). Rexburg, ID ranks 14th wettest of the 26 cities covered in Idaho.

Month by month in Rexburg

Month	Rain (in)	Off the roof (gal)	Garden shortfall (gal)
Jan	1.22	970
Feb	0.78	620
Mar	0.92	731
Apr	1.16	922	398
May	1.81	1,439	317
Jun	1.49	1,184	357
Jul	0.59	469	469
Aug	0.70	556	455
Sep	1.04	827	413
Oct	1.13	898	401
Nov	0.71	564
Dec	1.08	858

May is the wettest month (1.81 in, 1,439 gal off the roof); Jul the driest (0.59 in). Garden shortfall is what a 200 sq ft vegetable bed needs beyond the rain that lands on it, April to October.

What size rain barrel for Rexburg

Best fit: 3 linked 55-gallon barrels, which delivers about 2,427 gallons to the garden in a normal year (86.4% of its need).

If you buy one, link barrels with a short hose at the base so they fill and drain together, and check the overflow points away from the house.

Tank	Water used (gal/yr)	Spills over (gal/yr)
55 gal	1,343	8,080
110 gal	2,163	7,260
165 gal	2,427	6,996
275 gal	2,503	6,920
550 gal	2,503	6,920
1,000 gal	2,503	6,920
1,500 gal	2,503	6,920
2,500 gal	2,503	6,920
5,000 gal	2,503	6,920

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 Idaho?

Allowed through a legal clarification made by the Office of the Attorney General

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