Yes, rainwater collection is legal in Colorado, but subject to strict state and local regulations, particularly under the 2009 Water Rights Determination and Administration Act and recent 2026 compliance updates. Residential systems under 10,000 gallons are generally permitted, while larger volumes trigger prior-appropriation review by the Colorado Division of Water Resources (DWR). Local municipalities may impose additional permitting requirements, such as Denver Water’s 2024 stormwater management guidelines.
Key Regulations for Rainwater Collection in Colorado
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Prior-appropriation doctrine compliance: Systems exceeding 10,000 gallons or diverting from natural streams require DWR approval to avoid impairment of downstream water rights. The 2026 amendments to Rule 10.1 now mandate pre-construction hydrological impact assessments for mid-sized systems (5,000–10,000 gallons).
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Local permitting mandates: Counties like Boulder and Jefferson require building permits for storage tanks over 500 gallons, with stormwater detention standards enforced by the respective county floodplain administrators. Denver’s 2024 Stormwater Criteria Manual prohibits roof runoff from entering combined sewer systems unless treated via approved filtration.
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Use restrictions: Collected water may only be used for non-potable purposes (irrigation, toilet flushing, or laundry) unless treated to EPA drinking water standards. The Colorado Department of Public Health & Environment (CDPHE) 2025 guidelines prohibit untreated rainwater for potable uses without a variance, which is rarely granted.