St. Marys, GA rainwater: 44,938 gallons off a roof
Rainwater from a roof in St. Marys, GA
44,938gallons a year
That is a 1,500 sq ft asphalt roof under St. Marys, GA's normal 56.5 inches of rain, about 795 gallons for every inch that falls.
In St. Marys, 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 Kingsland 3.1 Ne station (4.9 mi away). St. Marys, GA ranks 5th wettest of the 101 cities covered in Georgia.
Month by month in St. Marys
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 3.21 | 2,551 | |
| Feb | 2.92 | 2,321 | |
| Mar | 3.40 | 2,702 | |
| Apr | 3.31 | 2,631 | 130 |
| May | 4.78 | 3,799 | |
| Jun | 7.65 | 6,080 | |
| Jul | 7.23 | 5,746 | |
| Aug | 7.08 | 5,627 | |
| Sep | 7.01 | 5,572 | |
| Oct | 4.32 | 3,434 | 4 |
| Nov | 2.51 | 1,995 | |
| Dec | 3.12 | 2,480 |
Jun is the wettest month (7.65 in, 6,080 gal off the roof); Nov the driest (2.51 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 St. Marys
Best fit: one 55-gallon barrel, which delivers about 111 gallons to the garden in a normal year (83.2% 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 St. Marys's roof water will pass straight through it.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 111 | 43,792 |
| 110 gal | 111 | 43,792 |
| 165 gal | 111 | 43,792 |
| 275 gal | 111 | 43,792 |
| 550 gal | 111 | 43,792 |
| 1,000 gal | 111 | 43,792 |
| 1,500 gal | 111 | 43,792 |
| 2,500 gal | 111 | 43,792 |
| 5,000 gal | 111 | 43,792 |
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