Centennial, CO rainwater: 11,938 gallons off a roof
How much rain a roof in Centennial, CO collects
11,938gallons a year
That is a 1,500 sq ft asphalt roof under Centennial, CO's normal 15.0 inches of rain, about 795 gallons for every inch that falls.
In Centennial, CO 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 Denver Centennial Ap station (1.6 mi away). Centennial, CO ranks 35th wettest of the 53 cities covered in Colorado.
Month by month in Centennial
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 0.41 | 326 | |
| Feb | 0.43 | 342 | |
| Mar | 1.04 | 827 | |
| Apr | 1.94 | 1,542 | 300 |
| May | 2.04 | 1,621 | 288 |
| Jun | 1.98 | 1,574 | 295 |
| Jul | 1.76 | 1,399 | 323 |
| Aug | 2.25 | 1,788 | 262 |
| Sep | 1.29 | 1,025 | 382 |
| Oct | 1.00 | 795 | 418 |
| Nov | 0.53 | 421 | |
| Dec | 0.35 | 278 |
Aug is the wettest month (2.25 in, 1,788 gal off the roof); Dec the driest (0.35 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 Centennial?
Best fit: 2 linked 55-gallon barrels, which delivers about 1,928 gallons to the garden in a normal year (85.0% 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 Centennial's roof water will pass straight through it.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 1,552 | 9,816 |
| 110 gal | 1,928 | 9,440 |
| 165 gal (over cap) | 1,967 | 9,400 |
| 275 gal (over cap) | 1,967 | 9,400 |
| 550 gal (over cap) | 1,967 | 9,400 |
| 1,000 gal (over cap) | 1,967 | 9,400 |
| 1,500 gal (over cap) | 1,967 | 9,400 |
| 2,500 gal (over cap) | 1,967 | 9,400 |
| 5,000 gal (over cap) | 1,967 | 9,400 |
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 Colorado?
Most households may use rain barrels: a maximum of two rain barrels with a combined storage of 110 gallons or less per household, rooftop runoff only, used outdoors on the same property (HB16-1005). Larger rooftop collection only for qualifying well-permit holders (SB09-080) or pilot projects (HB09-1129).
Checked against the current source on 2026-11-06. Source