Two barrels. A hundred and ten gallons. That's the deal.
Residential rainwater collection was effectively illegal in Colorado until 2016, when HB16-1005 carved out a narrow exception for homeowners. Here are the rules, plainly.
Why It's Weird Here
Colorado runs on prior-appropriation water law — “first in time, first in right.” Whoever put the water to beneficial use earliest holds the most senior claim, and senior claims get satisfied before junior ones.
Under that doctrine, the rain that lands on your roof is, in legal theory, already spoken for: it would otherwise run off, reach a stream, and feed the rights of downstream senior holders. That is why capturing it was restricted for so long, and why the 2016 exception is written as narrowly as it is.
The Rules
- Maximum 2 barrels, 110 gallons combined — per household or building, not per unit.
- Single-family homes and multi-family buildings of four units or fewer only.
- Rooftop downspout collection only.
- Outdoor use only, on the same property where it was collected.
- Not potable — untreated roof runoff is not safe to drink.
- Barrels must have a sealable lid, for mosquito and contamination control.
- HOAs cannot prohibit rain barrels.
Exempt-well owners may apply for a Rooftop Precipitation Collection System Permit to exceed 110 gallons. This is niche — most households do not need it.
Sources
- Colorado Water Conservation Board — the state agency overseeing water policy.
- Colorado HB16-1005 — the rain barrel bill itself.
- CSU Extension — rain barrel setup and usage guidance.