Colorado rainwater collection rules for homeowners

What the rule says

Colorado homeowners generally may collect rainwater from their rooftops, within clear
statutory limits. C.R.S. section 37-96.5-103,
part of the "Rooftop Precipitation Collection" article added by House Bill 16-1005 in
2016, permits rooftop precipitation collection when four conditions are met: no more
than two rain barrels with a combined storage capacity of 110 gallons or less are used;
the precipitation is collected from the rooftop of a building used primarily as a
single-family residence or a multi-family residence with four or fewer units; the
collected precipitation is used for outdoor purposes including irrigation of lawns
and gardens; and the precipitation is used on the residential property where it was
collected. A rain barrel is defined as a storage container with a sealable lid, located
aboveground outside of a residential home, used to collect precipitation from a rooftop
downspout (C.R.S. 37-96.5-102). The statute also declares that the use of a rain barrel
does not constitute a water right (C.R.S. 37-96.5-101(3)).

The Colorado Division of Water Resources (DWR), the state engineer's agency, confirms
on its website that no permit or other approval is required for capture and use in
rain barrels with a combined capacity of 110 gallons or less under C.R.S. 37-96.5-103,
and that barrels may be filled and refilled throughout the year. The water may not be
used for drinking water or indoor household purposes, and barrels must have sealable
lids to keep out insects and pests.

A separate, older path allows more extensive collection. C.R.S. 37-92-602(1)(g),
established by Senate Bill 09-080, exempts rooftop precipitation capture systems for
residences that are not served by a domestic water system serving more than three
single-family dwellings, with uses limited to ordinary household purposes, fire
protection, watering poultry, domestic animals, and livestock, and irrigation of not
more than one acre of gardens and lawns. DWR explains that a residence that has, or
could qualify for, an exempt or small-capacity residential well permit may collect
more than 110 gallons through this path — but a rooftop precipitation collection
permit (form GWS-78) is required first.

Which authority controls

The Colorado General Assembly sets the statewide rules through Title 37 (Water and
Irrigation) and Title 38 (Property). The state engineer, through the Division of Water
Resources, administers the program: it posts the required information on rain barrel
use (C.R.S. 37-96.5-104), can curtail rain barrel usage upon a finding of material
injury to water rights under C.R.S. 37-92-502(2)(a), and issues the GWS-78 permits for
well-linked capture. For homes in common interest communities, the Common Interest
Ownership Act (C.R.S. 38-33.3-106.5(1)(j)) controls what associations may prohibit.
Local governments remain the permit authority for construction, zoning, drainage, and
stormwater matters that apply to larger systems or to any installation a local code
regulates. For renters, the landlord's consent and the lease control placement, subject
to the same statutes.

What may still be required or restricted

• Common interest communities: an association may not prohibit the use of a rain
  barrel used in accordance with C.R.S. 37-96.5-103, but it may impose reasonable
  aesthetic requirements governing placement or external appearance, and the statute
  does not confer a right to place a barrel on property that is leased (without the
  lessor's permission), on a common element or limited common element, on
  association-maintained property, or attached to one or more other units without the
  other owners' permission.
• Larger systems: collecting beyond 110 gallons without the well-linked permit is
  not authorized by the reviewed sources; the exemption in C.R.S. 37-92-602(1)(g)
  requires a permit and the qualifying well status.
• Water rights: the state engineer may curtail rain barrel usage under C.R.S.
  37-92-502(2)(a), and violating a state engineer's order under the well-linked path
  can carry a fine of up to $500 per violation plus costs and attorney fees in an
  enforcement action.
• Local rules: municipal or county codes on drainage, overflow, stormwater, and
  permits can apply independently of the statewide allowance.
• Safety and maintenance: sealable lids are part of the statutory definition of a
  rain barrel and are needed to prevent mosquito breeding; DWR points to the Colorado
  State University Extension fact sheet for best practices.

Facts that could change the answer

The 110-gallon allowance applies only to buildings used primarily as single-family
residences or multi-family residences with four or fewer units, and only to outdoor
use on the property where the water is collected. Adding a third barrel, exceeding
110 gallons of combined capacity, using the water indoors, or collecting from a
building with more than four units moves the activity outside C.R.S. 37-96.5-103. The
well-linked exemption under C.R.S. 37-92-602(1)(g) is unavailable when the residence is
served by a domestic water system serving more than three single-family dwellings. The
statutes also change over time: HB 16-1005 amended Title 37 and Title 38 together in
2016, and the general assembly required the state engineer to report to the legislature
in 2019 and 2022 on whether small-scale residential precipitation collection caused
discernible injury to downstream water rights.

Practical decision path

1. Confirm the building is a single-family residence or a multi-family residence with
   four or fewer units, and that the barrel setup uses no more than two rain barrels
   with a combined capacity of 110 gallons or less.
2. Use the collected water only for outdoor purposes on the property where it was
   collected, and keep barrels sealed to prevent mosquitoes.
3. In an HOA or condo association, check the written rules for reasonable aesthetic
   requirements and confirm where the barrel may be placed; common elements, limited
   common elements, and leased areas require permission.
4. If you want to collect more than 110 gallons, check whether the property has, or
   could qualify for, an exempt or small-capacity residential well permit, and contact
   the Division of Water Resources about the rooftop precipitation collection permit
   (form GWS-78) before starting.
5. Ask the city or county building or water department whether any local permit,
   drainage, or stormwater rule applies to the planned system.

Records to keep

Keep receipts and specifications showing barrel count, combined capacity, and
sealable lids; the association's written rules and any written approval, denial, or
conditions about placement or appearance; any GWS-78 permit and well permit records
if collecting under the well-linked path; local permit or inspection records; and
dated correspondence with an association, landlord, or the Division of Water Resources
if questions or disputes arise.

When professional advice may help

Consider a qualified professional if an association denies or conditions a barrel
placement in a way you believe the statute does not allow, if you plan a system larger
than 110 gallons and need to establish well eligibility or obtain a GWS-78 permit, if
a water-rights or curtailment question arises, or if a local code or landlord dispute
involves the installation.

Before work begins, obtain the written requirement from the authority named in the guide and keep the record.