Grain Valley, MO rainwater: 34,606 gallons off a roof

Rainwater from a roof in Grain Valley, MO

34,606gallons a year

That is a 1,500 sq ft asphalt roof under Grain Valley, MO's normal 43.5 inches of rain, about 795 gallons for every inch that falls.

In Grain Valley, MO 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 Blue Springs 0.9 Nw station (3.9 mi away). Grain Valley, MO ranks 47th wettest of the 80 cities covered in Missouri.

Month by month in Grain Valley

Month	Rain (in)	Off the roof (gal)	Garden shortfall (gal)
Jan	1.55	1,232
Feb	1.68	1,335
Mar	2.92	2,321
Apr	4.39	3,489
May	5.76	4,578
Jun	4.96	3,942
Jul	5.94	4,721
Aug	4.10	3,259	31
Sep	4.56	3,624
Oct	3.43	2,726	115
Nov	2.46	1,955
Dec	1.79	1,423

Jul is the wettest month (5.94 in, 4,721 gal off the roof); Jan the driest (1.55 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 Grain Valley?

Best fit: one 55-gallon barrel, which delivers about 118 gallons to the garden in a normal year (80.9% 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 Grain Valley's roof water will pass straight through it.

Tank	Water used (gal/yr)	Spills over (gal/yr)
55 gal	118	33,543
110 gal	118	33,543
165 gal	118	33,543
275 gal	118	33,543
550 gal	118	33,543
1,000 gal	118	33,543
1,500 gal	118	33,543
2,500 gal	118	33,543
5,000 gal	118	33,543

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 Missouri?

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