Marietta, GA rainwater: 40,583 gallons off a roof
Rainwater from a roof in Marietta, GA
40,583gallons a year
That is a 1,500 sq ft asphalt roof under Marietta, GA's normal 51.1 inches of rain, about 795 gallons for every inch that falls.
In Marietta, 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 Smyrna 2.3 Ne station (5.0 mi away). Marietta, GA ranks 73rd wettest of the 101 cities covered in Georgia.
Month by month in Marietta
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 4.63 | 3,680 | |
| Feb | 4.57 | 3,632 | |
| Mar | 4.87 | 3,871 | |
| Apr | 4.26 | 3,386 | 11 |
| May | 3.79 | 3,012 | 70 |
| Jun | 4.17 | 3,314 | 22 |
| Jul | 4.81 | 3,823 | |
| Aug | 3.89 | 3,092 | 57 |
| Sep | 3.89 | 3,092 | 57 |
| Oct | 3.49 | 2,774 | 107 |
| Nov | 4.13 | 3,283 | |
| Dec | 4.56 | 3,624 |
Mar is the wettest month (4.87 in, 3,871 gal off the roof); Oct the driest (3.49 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 Marietta?
Best fit: one 55-gallon barrel, which delivers about 262 gallons to the garden in a normal year (80.5% 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 Marietta's roof water will pass straight through it.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 262 | 39,120 |
| 110 gal | 262 | 39,120 |
| 165 gal | 262 | 39,120 |
| 275 gal | 262 | 39,120 |
| 550 gal | 262 | 39,120 |
| 1,000 gal | 262 | 39,120 |
| 1,500 gal | 262 | 39,120 |
| 2,500 gal | 262 | 39,120 |
| 5,000 gal | 262 | 39,120 |
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