Johns Creek, GA rainwater: 43,698 gallons off a roof
Rainwater from a roof in Johns Creek, GA
43,698gallons a year
That is a 1,500 sq ft asphalt roof under Johns Creek, GA's normal 55.0 inches of rain, about 795 gallons for every inch that falls.
In Johns Creek, 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 Johns Creek 3.0 Ssw station (0.8 mi away). Johns Creek, GA ranks 17th wettest of the 101 cities covered in Georgia.
Month by month in Johns Creek
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 4.95 | 3,934 | |
| Feb | 4.81 | 3,823 | |
| Mar | 5.05 | 4,014 | |
| Apr | 3.94 | 3,132 | 51 |
| May | 4.04 | 3,211 | 39 |
| Jun | 4.61 | 3,664 | |
| Jul | 5.65 | 4,491 | |
| Aug | 4.40 | 3,497 | |
| Sep | 4.26 | 3,386 | 11 |
| Oct | 3.90 | 3,100 | 56 |
| Nov | 4.39 | 3,489 | |
| Dec | 4.98 | 3,958 |
Jul is the wettest month (5.65 in, 4,491 gal off the roof); Oct the driest (3.90 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 Johns Creek?
Best fit: one 55-gallon barrel, which delivers about 129 gallons to the garden in a normal year (82.1% of its need).
If you set one up, a 55-gallon barrel with a downspout diverter is the whole job. Check that the overflow points away from your foundation, because most of Johns Creek's roof water will pass straight through it.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 129 | 42,340 |
| 110 gal | 129 | 42,340 |
| 165 gal | 129 | 42,340 |
| 275 gal | 129 | 42,340 |
| 550 gal | 129 | 42,340 |
| 1,000 gal | 129 | 42,340 |
| 1,500 gal | 129 | 42,340 |
| 2,500 gal | 129 | 42,340 |
| 5,000 gal | 129 | 42,340 |
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