Roswell, GA rainwater: 42,506 gallons off a roof
Roswell, GA: gallons off the roof each year
42,506gallons a year
That is a 1,500 sq ft asphalt roof under Roswell, GA's normal 53.5 inches of rain, about 795 gallons for every inch that falls.
In Roswell, 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 Marietta 8.3 Ne station (4.1 mi away). Roswell, GA ranks 42nd wettest of the 101 cities covered in Georgia.
Month by month in Roswell
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 4.72 | 3,751 | |
| Feb | 4.76 | 3,783 | |
| Mar | 4.96 | 3,942 | |
| Apr | 4.50 | 3,577 | |
| May | 3.98 | 3,163 | 46 |
| Jun | 4.48 | 3,561 | |
| Jul | 4.91 | 3,902 | |
| Aug | 4.34 | 3,449 | 1 |
| Sep | 4.05 | 3,219 | 37 |
| Oct | 3.72 | 2,957 | 79 |
| Nov | 4.41 | 3,505 | |
| Dec | 4.65 | 3,696 |
Mar is the wettest month (4.96 in, 3,942 gal off the roof); Oct the driest (3.72 in). Garden shortfall is what a 200 sq ft vegetable bed needs beyond the rain that lands on it, April to October.
Which tank size is worth it in Roswell
Best fit: one 55-gallon barrel, which delivers about 135 gallons to the garden in a normal year (82.7% 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 Roswell's roof water will pass straight through it.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 135 | 41,141 |
| 110 gal | 135 | 41,141 |
| 165 gal | 135 | 41,141 |
| 275 gal | 135 | 41,141 |
| 550 gal | 135 | 41,141 |
| 1,000 gal | 135 | 41,141 |
| 1,500 gal | 135 | 41,141 |
| 2,500 gal | 135 | 41,141 |
| 5,000 gal | 135 | 41,141 |
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