It is illegal or heavily restricted to collect rainwater in certain U.S. states, primarily due to water rights laws that aim to protect downstream water users. Here are key points about where and how rainwater collection is regulated or illegal:
- Colorado is the state most known for strict restrictions. While it is a myth that rainwater harvesting is completely illegal, the state allows only two rain barrels per household with a maximum total capacity of 110 gallons, and the collected water must be used outdoors only (e.g., watering plants, washing cars). Larger-scale collection or use for drinking is prohibited. This law dates back over 120 years and is based on the doctrine that rainwater runoff belongs to downstream water rights holders
- Arkansas and Georgia require harvested rainwater systems to meet state plumbing codes and restrict collection for potable (drinking) use
- Idaho and Illinois restrict rainwater collection for potable use and may require permits or system designs by engineers
- Utah, Nevada, Kansas, Oregon, and Washington may require permits or have specific regulations for rainwater harvesting, especially for larger or commercial systems
- Many other states have no restrictions or actively encourage rainwater harvesting, sometimes offering incentives like tax credits or reduced stormwater fees
Internationally, for example in the UK, collecting rainwater is legal and encouraged, especially in drier regions, though regulations apply if the system is connected to mains water
. In summary, the only U.S. state with significant legal limits on rainwater collection is Colorado, with other states imposing varying levels of regulation mainly concerning potable use and system standards. The federal government does not regulate rainwater harvesting; it is governed at the state level
