With the passing of legislation in 2016, rainwater harvesting became legal for most homeowners in Colorado. The law allows rain barrels to be installed at single-family households and multifamily households with four or less units. A maximum of two barrels with the combined capacity of 110 gallons can be used at each household.

There are additional restrictions, says Colorado Rain Catcher manager Pamela Churman. “Rain barrels can only be used to capture rainwater from rooftop downspouts and the water must be used on the same property where it was captured. It can only be used for outdoor purposes such as watering lawns, plants and gardens,” she says. Untreated rainwater collected from roofs is not safe to drink.

Colorado was the only state to ban residential rain barrels and one of just four states restricting rainwater harvesting. The use of water here and in other western states is governed by “prior appropriation” water rights—a legal doctrine that controls the water supply. It’s a priority system of “first in time, first in right.” In an arid environment, every drop counts and water rights holders depend on snowmelt runoff and rainfall to supply their uses.

The Colorado Legislature had previously rejected the measure based on concerns that rain barrels could deprive downstream and/or senior water rights holders. However, a study conducted by the Colorado State University Colorado Stormwater Center found that most rainwater would be absorbed in the ground by the downspout, or in the ground in a garden, and would not end up in water supplies.

Any container capable of collecting the rain from a roof can be used as a rainwater harvesting system, but Colorado law requires the container have a sealable lid to prevent mosquito breeding grounds.

“It’s starting to catch on and we’re getting busier,” Churman says. Her company is lobbying to expand the law to include schools and businesses.

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