Ferndale, MI rainwater: 23,757 gallons off a roof

Ferndale, MI: gallons off the roof each year

23,757gallons a year

That is a 1,500 sq ft asphalt roof under Ferndale, MI's normal 29.9 inches of rain, about 795 gallons for every inch that falls.

In Ferndale, 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 Detroit City Ap station (7.1 mi away). Ferndale, MI ranks 87th wettest of the 90 cities covered in Michigan.

Month by month in Ferndale

Month	Rain (in)	Off the roof (gal)	Garden shortfall (gal)
Jan	1.45	1,152
Feb	1.41	1,121
Mar	2.02	1,606
Apr	2.82	2,241	191
May	3.49	2,774	107
Jun	3.10	2,464	156
Jul	3.22	2,559	141
Aug	3.10	2,464	156
Sep	3.09	2,456	157
Oct	2.30	1,828	256
Nov	2.16	1,717
Dec	1.73	1,375

May is the wettest month (3.49 in, 2,774 gal off the roof); Feb the driest (1.41 in). Garden shortfall is what a 200 sq ft vegetable bed needs beyond the rain that lands on it, April to October.

Which tank size is worth it in Ferndale

Best fit: one 55-gallon barrel, which delivers about 923 gallons to the garden in a normal year (79.3% of its need).

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

Tank	Water used (gal/yr)	Spills over (gal/yr)
55 gal	923	21,813
110 gal	923	21,813
165 gal	923	21,813
275 gal	923	21,813
550 gal	923	21,813
1,000 gal	923	21,813
1,500 gal	923	21,813
2,500 gal	923	21,813
5,000 gal	923	21,813

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