Farmington, UT rainwater: 13,997 gallons off a roof
Rainwater from a roof in Farmington, UT
13,997gallons a year
That is a 1,500 sq ft asphalt roof under Farmington, UT's normal 17.6 inches of rain, about 795 gallons for every inch that falls.
Farmington, UT has gaps between storms long enough to drain a single barrel. Around 165 gallons of storage catches most of what is worth catching.
Rainfall: NOAA 1991-2020 climate normals, the Farmington 1.8 W station (1.2 mi away). Farmington, UT ranks 45th wettest of the 67 cities covered in Utah.
Month by month in Farmington
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 1.75 | 1,391 | |
| Feb | 1.04 | 827 | |
| Mar | 1.79 | 1,423 | |
| Apr | 2.12 | 1,685 | 278 |
| May | 2.53 | 2,011 | 227 |
| Jun | 1.11 | 882 | 404 |
| Jul | 0.56 | 445 | 473 |
| Aug | 1.05 | 835 | 411 |
| Sep | 1.35 | 1,073 | 374 |
| Oct | 1.56 | 1,240 | 348 |
| Nov | 1.28 | 1,017 | |
| Dec | 1.47 | 1,168 |
May is the wettest month (2.53 in, 2,011 gal off the roof); Jul the driest (0.56 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 Farmington
Best fit: 3 linked 55-gallon barrels, which delivers about 2,103 gallons to the garden in a normal year (83.6% of its need).
If you buy one, link barrels with a short hose at the base so they fill and drain together, and check the overflow points away from the house.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 1,194 | 12,067 |
| 110 gal | 1,816 | 11,446 |
| 165 gal | 2,103 | 11,158 |
| 275 gal | 2,235 | 11,026 |
| 550 gal | 2,235 | 11,026 |
| 1,000 gal | 2,235 | 11,026 |
| 1,500 gal | 2,235 | 11,026 |
| 2,500 gal | 2,235 | 11,026 |
| 5,000 gal (over cap) | 2,235 | 11,026 |
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 Utah?
Up to 2 covered containers of max 100 gal each with no registration; with free registration at the Utah Division of Water Rights, total storage up to 2,500 gal. Use limited to the same parcel where captured.
Checked against the current source on 2026-11-06. Source