Lebanon, NH rainwater: 30,258 gallons off a roof

Rainwater from a roof in Lebanon, NH

30,258gallons a year

That is a 1,500 sq ft asphalt roof under Lebanon, NH's normal 38.1 inches of rain, about 795 gallons for every inch that falls.

In Lebanon, NH 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 Lebanon Muni Ap station (2.6 mi away). Lebanon, NH ranks 11th wettest of the 11 cities covered in New Hampshire.

Month by month in Lebanon

Month	Rain (in)	Off the roof (gal)	Garden shortfall (gal)
Jan	2.29	1,820
Feb	2.10	1,669
Mar	2.70	2,146
Apr	2.99	2,376	170
May	3.32	2,639	128
Jun	3.80	3,020	69
Jul	3.99	3,171	45
Aug	3.62	2,877	91
Sep	3.44	2,734	113
Oct	4.00	3,179	44
Nov	2.98	2,369
Dec	2.84	2,257

Oct is the wettest month (4.00 in, 3,179 gal off the roof); Feb the driest (2.10 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 Lebanon?

Best fit: one 55-gallon barrel, which delivers about 506 gallons to the garden in a normal year (76.7% of its need).

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

Tank	Water used (gal/yr)	Spills over (gal/yr)
55 gal	506	28,583
110 gal	506	28,583
165 gal	506	28,583
275 gal	506	28,583
550 gal	506	28,583
1,000 gal	506	28,583
1,500 gal	506	28,583
2,500 gal	506	28,583
5,000 gal	506	28,583

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 New Hampshire?

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