Chester, PA rainwater: 33,104 gallons off a roof

Rainwater from a roof in Chester, PA

33,104gallons a year

That is a 1,500 sq ft asphalt roof under Chester, PA's normal 41.7 inches of rain, about 795 gallons for every inch that falls.

In Chester, PA 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 Marcus Hook station (3.3 mi away). Chester, PA ranks 52nd wettest of the 68 cities covered in Pennsylvania.

Month by month in Chester

Month	Rain (in)	Off the roof (gal)	Garden shortfall (gal)
Jan	3.15	2,504
Feb	2.22	1,764
Mar	3.93	3,124
Apr	3.48	2,766	108
May	3.16	2,512	148
Jun	3.31	2,631	130
Jul	4.81	3,823
Aug	3.68	2,925	84
Sep	4.36	3,465
Oct	3.69	2,933	82
Nov	2.61	2,074
Dec	3.25	2,583

Jul is the wettest month (4.81 in, 3,823 gal off the roof); Feb the driest (2.22 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 Chester?

Best fit: one 55-gallon barrel, which delivers about 449 gallons to the garden in a normal year (81.3% 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 Chester's roof water will pass straight through it.

Tank	Water used (gal/yr)	Spills over (gal/yr)
55 gal	449	31,649
110 gal	449	31,649
165 gal	449	31,649
275 gal	449	31,649
550 gal	449	31,649
1,000 gal	449	31,649
1,500 gal	449	31,649
2,500 gal	449	31,649
5,000 gal	449	31,649

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 Pennsylvania?

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