Maryville, TN rainwater: 42,912 gallons off a roof

Rainwater from a roof in Maryville, TN

42,912gallons a year

That is a 1,500 sq ft asphalt roof under Maryville, TN's normal 54.0 inches of rain, about 795 gallons for every inch that falls.

In Maryville, TN 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 Maryville 3.4 Ese station (3.8 mi away). Maryville, TN ranks 49th wettest of the 65 cities covered in Tennessee.

Month by month in Maryville

Month	Rain (in)	Off the roof (gal)	Garden shortfall (gal)
Jan	4.31	3,426
Feb	4.75	3,775
Mar	5.07	4,030
Apr	4.71	3,744
May	4.29	3,410	7
Jun	4.87	3,871
Jul	5.82	4,626
Aug	4.00	3,179	44
Sep	3.89	3,092	57
Oct	2.77	2,202	197
Nov	4.19	3,330
Dec	5.32	4,228

Jul is the wettest month (5.82 in, 4,626 gal off the roof); Oct the driest (2.77 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 Maryville?

Best fit: one 55-gallon barrel, which delivers about 253 gallons to the garden in a normal year (82.8% 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 Maryville's roof water will pass straight through it.

Tank	Water used (gal/yr)	Spills over (gal/yr)
55 gal	253	41,339
110 gal	253	41,339
165 gal	253	41,339
275 gal	253	41,339
550 gal	253	41,339
1,000 gal	253	41,339
1,500 gal	253	41,339
2,500 gal	253	41,339
5,000 gal	253	41,339

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 Tennessee?

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