Decatur, GA rainwater: 42,276 gallons off a roof
Rainwater from a roof in Decatur, GA
42,276gallons a year
That is a 1,500 sq ft asphalt roof under Decatur, GA's normal 53.2 inches of rain, about 795 gallons for every inch that falls.
In Decatur, 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 Decatur 1.2 Se station (1.1 mi away). Decatur, GA ranks 47th wettest of the 101 cities covered in Georgia.
Month by month in Decatur
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 4.79 | 3,807 | |
| Feb | 4.76 | 3,783 | |
| Mar | 4.88 | 3,879 | |
| Apr | 4.10 | 3,259 | 31 |
| May | 3.86 | 3,068 | 61 |
| Jun | 4.60 | 3,656 | |
| Jul | 5.11 | 4,061 | |
| Aug | 4.71 | 3,744 | |
| Sep | 3.86 | 3,068 | 61 |
| Oct | 3.42 | 2,718 | 116 |
| Nov | 4.13 | 3,283 | |
| Dec | 4.97 | 3,950 |
Jul is the wettest month (5.11 in, 4,061 gal off the roof); Oct the driest (3.42 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 Decatur?
Best fit: one 55-gallon barrel, which delivers about 223 gallons to the garden in a normal year (82.8% 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 Decatur's roof water will pass straight through it.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 223 | 40,883 |
| 110 gal | 223 | 40,883 |
| 165 gal | 223 | 40,883 |
| 275 gal | 223 | 40,883 |
| 550 gal | 223 | 40,883 |
| 1,000 gal | 223 | 40,883 |
| 1,500 gal | 223 | 40,883 |
| 2,500 gal | 223 | 40,883 |
| 5,000 gal | 223 | 40,883 |
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