RoofRainYield

Cumberland, MD rainwater: 31,172 gallons off a roof

Rainwater from a roof in Cumberland, MD

31,172gallons a year

That is a 1,500 sq ft asphalt roof under Cumberland, MD's normal 39.2 inches of rain, about 795 gallons for every inch that falls.

In Cumberland, MD 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 Cumberland 2 station (0.7 mi away). Cumberland, MD ranks 23rd wettest of the 23 cities covered in Maryland.

Month by month in Cumberland

MonthRain (in)Off the roof (gal)Garden shortfall (gal)
Jan2.792,218
Feb2.381,892
Mar3.422,718
Apr3.412,710117
May4.223,35416
Jun3.873,07660
Jul3.732,96577
Aug3.402,702118
Sep3.552,822100
Oct2.822,241191
Nov2.582,051
Dec3.052,424

May is the wettest month (4.22 in, 3,354 gal off the roof); Feb the driest (2.38 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 Cumberland

Best fit: one 55-gallon barrel, which delivers about 526 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 Cumberland's roof water will pass straight through it.

TankWater used (gal/yr)Spills over (gal/yr)
55 gal52629,431
110 gal52629,431
165 gal52629,431
275 gal52629,431
550 gal52629,431
1,000 gal52629,431
1,500 gal52629,431
2,500 gal52629,431
5,000 gal52629,431

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 Maryland?

No statewide rainwater harvesting regulations; check county for local incentives

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