Indianapolis, IN rainwater: 32,762 gallons off a roof
How much rain a roof in Indianapolis, IN collects
32,762gallons a year
That is a 1,500 sq ft asphalt roof under Indianapolis, IN's normal 41.2 inches of rain, about 795 gallons for every inch that falls.
In Indianapolis, IN 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 Indianapolis Zoo station (2.1 mi away). Indianapolis, IN ranks 56th wettest of the 88 cities covered in Indiana.
Month by month in Indianapolis
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 3.28 | 2,607 | |
| Feb | 2.17 | 1,725 | |
| Mar | 3.37 | 2,678 | |
| Apr | 3.83 | 3,044 | 65 |
| May | 4.41 | 3,505 | |
| Jun | 4.99 | 3,966 | |
| Jul | 4.16 | 3,306 | 24 |
| Aug | 2.62 | 2,082 | 216 |
| Sep | 3.12 | 2,480 | 153 |
| Oct | 3.05 | 2,424 | 162 |
| Nov | 3.35 | 2,663 | |
| Dec | 2.87 | 2,281 |
Jun is the wettest month (4.99 in, 3,966 gal off the roof); Feb the driest (2.17 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 Indianapolis
Best fit: one 55-gallon barrel, which delivers about 513 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 Indianapolis's roof water will pass straight through it.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 513 | 31,168 |
| 110 gal | 513 | 31,168 |
| 165 gal | 513 | 31,168 |
| 275 gal | 513 | 31,168 |
| 550 gal | 513 | 31,168 |
| 1,000 gal | 513 | 31,168 |
| 1,500 gal | 513 | 31,168 |
| 2,500 gal | 513 | 31,168 |
| 5,000 gal | 513 | 31,168 |
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 Indiana?
No statewide rainwater harvesting regulations; check county for local incentives
From the 2015 (Pacific Northwest National Laboratory report 24347); not yet re-checked against current law, so check with your state water agency before building anything large. Source