Trenton, MI rainwater: 29,734 gallons off a roof

Rainwater from a roof in Trenton, MI

29,734gallons a year

That is a 1,500 sq ft asphalt roof under Trenton, MI's normal 37.4 inches of rain, about 795 gallons for every inch that falls.

In Trenton, 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 Wyandotte station (5.0 mi away). Trenton, MI ranks 17th wettest of the 90 cities covered in Michigan.

Month by month in Trenton

Month	Rain (in)	Off the roof (gal)	Garden shortfall (gal)
Jan	2.51	1,995
Feb	2.15	1,709
Mar	2.67	2,122
Apr	3.36	2,671	123
May	4.14	3,290	26
Jun	3.39	2,694	120
Jul	3.92	3,116	54
Aug	3.71	2,949	80
Sep	3.45	2,742	112
Oct	2.84	2,257	188
Nov	2.75	2,186
Dec	2.52	2,003

May is the wettest month (4.14 in, 3,290 gal off the roof); Feb the driest (2.15 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 Trenton

Best fit: one 55-gallon barrel, which delivers about 545 gallons to the garden in a normal year (77.5% 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 Trenton's roof water will pass straight through it.

Tank	Water used (gal/yr)	Spills over (gal/yr)
55 gal	545	27,989
110 gal	545	27,989
165 gal	545	27,989
275 gal	545	27,989
550 gal	545	27,989
1,000 gal	545	27,989
1,500 gal	545	27,989
2,500 gal	545	27,989
5,000 gal	545	27,989

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