Suwanee, GA rainwater: 43,325 gallons off a roof
Rainwater from a roof in Suwanee, GA
43,325gallons a year
That is a 1,500 sq ft asphalt roof under Suwanee, GA's normal 54.5 inches of rain, about 795 gallons for every inch that falls.
In Suwanee, GA 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 Suwanee 1.5 W station (1.8 mi away). Suwanee, GA ranks 21st wettest of the 101 cities covered in Georgia.
Month by month in Suwanee
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 4.84 | 3,847 | |
| Feb | 4.73 | 3,759 | |
| Mar | 5.07 | 4,030 | |
| Apr | 3.97 | 3,155 | 47 |
| May | 4.34 | 3,449 | 1 |
| Jun | 4.99 | 3,966 | |
| Jul | 4.68 | 3,720 | |
| Aug | 4.67 | 3,712 | |
| Sep | 4.18 | 3,322 | 21 |
| Oct | 3.82 | 3,036 | 66 |
| Nov | 4.49 | 3,569 | |
| Dec | 4.73 | 3,759 |
Mar is the wettest month (5.07 in, 4,030 gal off the roof); Oct the driest (3.82 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 Suwanee
Best fit: one 55-gallon barrel, which delivers about 113 gallons to the garden in a normal year (83.2% 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 Suwanee's roof water will pass straight through it.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 113 | 41,981 |
| 110 gal | 113 | 41,981 |
| 165 gal | 113 | 41,981 |
| 275 gal | 113 | 41,981 |
| 550 gal | 113 | 41,981 |
| 1,000 gal | 113 | 41,981 |
| 1,500 gal | 113 | 41,981 |
| 2,500 gal | 113 | 41,981 |
| 5,000 gal | 113 | 41,981 |
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 Georgia?
Legal. Outdoor irrigation use is unrestricted; indoor non-potable systems must follow Appendix I 'Rainwater Recycling Systems' of the Georgia amendments to the state plumbing code. No state storage cap; potable use depends on local rules.
Checked against the current source on 2026-11-06. Source