Rainwater Harvesting Laws by State

Colorado law allows a maximum of 2 rain barrels with a combined capacity of 110 gallons or less. The collection must come from the rooftop of an eligible residence and the water must be used on that same residential property.

Colorado is the only state on this page with a hard statewide number that small. That 110-gallon ceiling is why Colorado anchors the red end of the map.

Utah allows up to 2,500 gallons of stored precipitation under Utah Code 73-3-1.5. A person can stay unregistered only with no more than 2 covered containers and no container above 100 gallons.

Registration starts once a Utah system goes above 2 covered containers or above 100 gallons in a single container. There is no fee for that registration according to the state registration page.

California and Washington sit between the green majority and the tight Colorado model. California uses a 360-gallon threshold for common small rain barrel setups and allows some outdoor non-spray systems up to 5,000 gallons without a permit, while Washington commonly treats 360 gallons as the small exterior no-permit line.

Wisconsin, Arkansas, South Carolina, South Dakota, and Wyoming are yellow Conditional states on this map. Their rows flag indoor plumbing, potable use, or permit triggers rather than one statewide gallon cap.