Berkley, MI rainwater: 26,244 gallons off a roof

Rainwater from a roof in Berkley, MI

26,244gallons a year

That is a 1,500 sq ft asphalt roof under Berkley, MI's normal 33.0 inches of rain, about 795 gallons for every inch that falls.

In Berkley, MI 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 Farmington station (9.3 mi away). Berkley, MI ranks 77th wettest of the 90 cities covered in Michigan.

Month by month in Berkley

Month	Rain (in)	Off the roof (gal)	Garden shortfall (gal)
Jan	2.34	1,860
Feb	1.75	1,391
Mar	2.07	1,645
Apr	3.05	2,424	162
May	3.61	2,869	92
Jun	3.31	2,631	130
Jul	3.21	2,551	142
Aug	3.17	2,520	147
Sep	3.35	2,663	125
Oct	2.65	2,106	212
Nov	2.48	1,971
Dec	2.03	1,613

May is the wettest month (3.61 in, 2,869 gal off the roof); Feb the driest (1.75 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 Berkley?

Best fit: one 55-gallon barrel, which delivers about 782 gallons to the garden in a normal year (77.4% 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 Berkley's roof water will pass straight through it.

Tank	Water used (gal/yr)	Spills over (gal/yr)
55 gal	782	24,293
110 gal	782	24,293
165 gal	782	24,293
275 gal	782	24,293
550 gal	782	24,293
1,000 gal	782	24,293
1,500 gal	782	24,293
2,500 gal	782	24,293
5,000 gal	782	24,293

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 Michigan?

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