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Collecting rainwater in Colorado
Yes, within limits. Since August 10, 2016, any Colorado single-family home — or a multi-family building with four or fewer units — may collect rain from its own rooftop in no more than two rain barrels holding 110 gallons combined, with no permit and no application, and use that water outdoors on the same property. C.R.S. § 37-96.5-103
A second, much larger allowance exists that most guides miss: a home served by its own well — or one that could qualify for a well permit — may collect rooftop precipitation with no gallon limit at all, though that route does require a permit from the state. C.R.S. § 37-90-105(1)(f)
The two-barrel rule
This is the rule almost everyone means when they ask whether rain barrels are legal in Colorado. It lives in Article 96.5 of Title 37, which the legislature added in 2016. Four conditions have to be true at once:
Precipitation from a rooftop may be collected if: (a) No more than two rain barrels with a combined storage capacity of one hundred ten gallons or less are utilized; (b) Precipitation is collected from the rooftop of a building that is used primarily as a single-family residence or a multi-family residence with four or fewer units; (c) The collected precipitation is used for outdoor purposes including irrigation of lawns and gardens; and (d) The collected precipitation is used on the residential property on which the precipitation is collected.
Read them closely, because three of the four are where people go wrong. The 110 gallons is a combined cap across both barrels — two 55-gallon drums is the canonical setup, and a single 110-gallon cistern is fine, but three barrels of any size is not. The water has to come off a roof, not out of a gutter at the bottom of a driveway or off a hillside. And it has to be used on the same property it fell on: you cannot haul it to a community garden across town.
What you can do with it is broad. The statute says "outdoor purposes including irrigation of lawns and gardens," and the Division of Water Resources reads that to cover car washing, watering livestock, and filling a hot tub, with the sensible caveat that you should judge whether roof runoff is clean enough for the use you have in mind. DWR · verified Jul. 2026
There is one flat prohibition:
A person shall not use precipitation collected under this article for drinking water or indoor household purposes.
No drinking, and nothing indoors — not even flushing a toilet or running a washing machine.
What counts as a "rain barrel," and as a "single-family residence"
Both terms are defined, and the definitions matter more than they look.
"Rain barrel" means a storage container with a sealable lid that is: (a) Located aboveground outside of a residential home; and (b) Used for collecting precipitation from a downspout of a rooftop. "Single-family residence" means a private residence that is a separate building or an individual residence that is part of a row of residences joined by common sidewalls.
A sealable lid is not a suggestion — it is part of the legal definition, and it is also the mosquito answer. An open stock tank collecting roof runoff is not a rain barrel under this statute. Buried cisterns are out too: the container has to sit aboveground and outside.
The residence definition is the quietly generous part. Townhomes, duplexes, and triplexes joined by common sidewalls each count as their own single-family residence, so each unit in a row of townhomes gets its own 110 gallons.
The bigger allowance, for homes on a well
Seven years before the rain barrel law, a different statute already let some Colorado homes collect rooftop precipitation — and it has no gallon cap. It applies to residences with an exempt or small-capacity residential well, or that could qualify for one.
Any system or method of collecting precipitation from the roof of a building that is used primarily as a residence and is not served by, whether or not connected to, a domestic water system that serves more than three single-family dwellings, but only if the use of the water so collected is limited to one or more of the following: (A) Ordinary household purposes; (B) Fire protection; (C) The watering of poultry, domestic animals, and livestock on farms and ranches; or (D) The irrigation of not more than one acre of gardens and lawns.
Compare that list to the barrel rule and the difference is stark: this route allows indoor household use, fire protection storage, and livestock water, in any volume, limited only by the one-acre cap on lawn and garden irrigation. The trade is paperwork. Anyone using it has to either file a notice describing the collection system alongside an existing well permit, include it on a new well permit application, or — if they will not actually drill a well — apply for a standalone rooftop precipitation collection permit. DWR handles all three on form GWS-78. DWR · verified Jul. 2026
The two routes side by side
| Rain barrels | Well-owner collection | |
|---|---|---|
| Statute | § 37-96.5-103 | § 37-90-105(1)(f), § 37-92-602(1)(g) |
| Who qualifies | Single-family home, or 4 units or fewer | Home with, or eligible for, an exempt well; not on a system serving 3+ other dwellings |
| How much | 110 gallons across two barrels | No volume cap |
| Permit | None | Yes — notice or permit, form GWS-78 |
| Indoor use | Prohibited | Allowed, per the well permit |
| Irrigation limit | Outdoors, same property | Up to one acre of lawn and garden |
Why this was ever a question
Rain barrels are a legal curiosity in Colorado because rain that falls on your roof is not, legally speaking, yours. Colorado water is public property, and it is allocated by the doctrine of prior appropriation — the older right gets water first, all the way down the river. Water intercepted on a rooftop is water that does not reach the ditch of someone whose decree may date to the 1870s. The legislature said so explicitly when it created the rain barrel law:
The general assembly hereby finds and determines that, pursuant to sections 5 and 6 of article XVI of the state constitution, water is considered the property of the public, is dedicated to the use of the people, is subject to the doctrine of prior appropriation, and must be administered in accordance with the priority system established in article 92 of this title. The general assembly declares that nothing in this article is intended to infringe upon or impair the doctrine of prior appropriation. The general assembly further declares that the use of a rain barrel does not constitute a water right.
Three consequences follow from that last sentence, and they are worth understanding before you buy a barrel. Your rain barrel is not a water right: it earns no priority date, it adds nothing to your property's value, and it conveys nothing to a buyer. It cannot be enlarged into a right by using it for years. And it is legally subordinate to every decreed right on your stream, which is why the statute hands the state a shut-off valve:
The state engineer may curtail rain barrel usage pursuant to section 37-92-502 (2)(a).
That cross-reference points to the division engineer's standing power to order diversions discontinued when they cause material injury to senior rights. In practice no Colorado homeowner has been ordered to empty a rain barrel, and the statute required the state engineer to report to the legislature in 2019 and 2022 on whether small-scale collection had caused any discernible injury downstream. C.R.S. § 37-96.5-105 But the authority is real, and it is the reason the rule is written as narrowly as it is.
If you are working out what your household may legally do with water — a barrel, a well, a lawn — the rest of the wells and home section covers the neighboring rules.
Common questions
Is it illegal to collect rainwater in Colorado?
No. Rooftop rainwater collection has been legal statewide since August 10, 2016, when HB 16-1005 took effect. Before that date Colorado had no statute authorizing residential rain barrels, which is the source of the persistent belief that they are banned. Collection is legal within the limits of C.R.S. § 37-96.5-103: two barrels, 110 gallons combined, rooftop source, outdoor use on the same property.
How many rain barrels can I have in Colorado?
Two, holding no more than 110 gallons combined. The cap is on total capacity, not on each barrel, so two 55-gallon drums is the standard setup and a single 110-gallon container is equally fine. You may fill and refill them as many times as it rains throughout the year — the 110 gallons is a storage limit, not an annual allowance.
Do I need a permit for a rain barrel in Colorado?
No permit or approval of any kind is required for rain barrels within the 110-gallon limit. A permit is only required for the separate, larger well-owner collection allowance under C.R.S. § 37-90-105(1)(f), which is filed with the Division of Water Resources on form GWS-78.
Can I drink water from a rain barrel, or use it indoors?
No. C.R.S. § 37-96.5-103(2) prohibits using rain barrel water for drinking water or any indoor household purpose, including toilet flushing and laundry. Homes collecting under the separate well-owner provision may use collected water for ordinary household purposes, because that use is authorized by the underlying well permit.
Can I install a cistern larger than 110 gallons?
Not under the rain barrel statute, which caps combined storage at 110 gallons and requires aboveground barrels with sealable lids. Larger rooftop collection is available to homes with, or eligible for, an exempt well under C.R.S. § 37-90-105(1)(f) — that provision has no volume cap but requires a permit. Any other large-scale collection needs a decreed water right, and usually a plan for augmentation.
Does a rain barrel give me a water right?
No. C.R.S. § 37-96.5-101(3) states that the use of a rain barrel does not constitute a water right. It carries no priority date, cannot ripen into a right through years of use, and transfers nothing to a buyer when you sell the property.
Primary sources
- C.R.S. §§ 37-96.5-101 to -105 — Rooftop Precipitation Collection (Title 37, official text) C.R.S. 2025 edition; article added 2016, unamended since
- HB 16-1005 — Residential Precipitation Collection, Colorado General Assembly effective Aug. 10, 2016
- C.R.S. § 37-90-105(1)(f) — rooftop precipitation capture with an exempt well (Title 37, official text) added by SB 09-080, effective July 1, 2009
- Colorado Division of Water Resources — Rainwater, Storm Water & Graywater state guidance and form GWS-78; read July 22, 2026