No, it is not illegal to collect rainwater in Oregon. State law specifically exempts rainwater harvested from an artificial impervious surface, such as a rooftop, from Oregon’s water rights permit system.1Oregon State Legislature. Oregon Revised Statutes 537.141 – Uses of Water Not Requiring Water Right Application, Permit or Certificate You don’t need a permit from the Oregon Water Resources Department, and the exemption covers both residential and commercial properties. What can change is whether you need a plumbing or building permit, and that depends on how you plan to use the water and how much you store.
What the Rainwater Exemption Actually Covers
ORS 537.141 lists water uses that sit outside Oregon’s permit process, and one of them is “the collection of precipitation water from an artificial impervious surface and the use of such water.”1Oregon State Legislature. Oregon Revised Statutes 537.141 – Uses of Water Not Requiring Water Right Application, Permit or Certificate The exemption hinges on two conditions. The water must be precipitation, meaning rain or snow. And it must be collected from an artificial impervious surface before it touches the ground. Oregon’s Building Codes Division limits harvesting to roof surfaces in practice.2Oregon Building Codes Division. Oregon Smart Guide – Facts About Rainwater Harvesting in Oregon
A standard setup works like this: gutters and downspouts channel rain from your roof into a barrel or cistern. As long as the water goes straight from the roof into your storage container without contacting soil along the way, you’re within the exemption. The scale doesn’t matter for the water rights question. A single rain barrel and a commercial cistern have the same legal standing.
What You Can Legally Do With Collected Rainwater
Legality of collection is one question. Legality of use is another, and it turns on where the water ends up.
Outdoor Use
Watering a garden, irrigating landscaping, or washing a car with rainwater from a barrel requires no permits at all. No treatment is required. Since the water never enters your home’s plumbing, the plumbing code doesn’t come into play.
Indoor Non-Potable Use
You can pipe rainwater inside for uses like flushing toilets or running a washing machine, but this requires a plumbing permit because the system connects to your building’s plumbing. Chapter 16 of the Oregon Plumbing Specialty Code governs non-potable rainwater catchment systems. It requires backflow prevention devices and labeling on tanks warning that the water is not safe to drink.2Oregon Building Codes Division. Oregon Smart Guide – Facts About Rainwater Harvesting in Oregon Backflow prevention keeps rainwater from flowing back into your municipal water supply if pressure drops.
Drinking Water
Using rainwater for drinking or cooking is allowed, but the requirements are much stricter. The system must be designed by a licensed or registered design professional, and you’ll need a plumbing permit from your local building department. Appendix K of the Oregon Plumbing Specialty Code covers potable rainwater catchment.
The professional design requirement exists for a reason. The CDC warns that roofing materials, gutters, and piping can introduce chemicals like lead, copper, and asbestos into collected water, and bird droppings and debris add bacteria.3Centers for Disease Control and Prevention. Collecting Rainwater and Your Health: An Overview Untreated rooftop rainwater is not safe to drink. Proper filtration, disinfection, and testing are what make it safe.
When a Building Permit Comes Into Play
The water rights exemption applies regardless of tank size. Local building codes are a separate matter. Storage tanks over 5,000 gallons are more likely to trigger a building permit requirement from your local building department. The exact threshold and conditions vary by jurisdiction and depend on site factors like slope and proximity to other structures. A tank that large is heavy enough to need a proper foundation, and local officials want to confirm it won’t create a structural hazard. Check with your city or county building department before installing a large system.
Where the Exemption Stops
The rainwater exemption is narrow. It covers only precipitation captured from an artificial surface before the water hits the ground. Once water enters a natural waterway or soaks into the earth, it becomes part of Oregon’s regulated water system, and using it without a water right permit is illegal.
This is where rural property owners often get tripped up. Owning land with a creek running through it does not give you the right to use that water. Under Oregon’s prior appropriation system, anyone who wants to use surface water or groundwater must get a permit from the Oregon Water Resources Department.4Oregon Water Resources Department. Water Right Permit Application Guidebook – Surface Water The following all fall outside the rainwater exemption:
- Streams, creeks, and springs, even ones flowing entirely through your property. These require a surface water permit.5Oregon Water Resources Department. Apply for a Water Use Permit
- Ponds and reservoirs built to capture surface runoff. These require a reservoir permit.
- Groundwater and wells. Drilling a well requires a groundwater permit.5Oregon Water Resources Department. Apply for a Water Use Permit
Penalties for Using Water Without a Permit
Diverting or using surface water or groundwater without a valid permit is a Class B misdemeanor. Possessing or using water without a legally acquired right is prima facie evidence of guilt, meaning the state doesn’t need to prove you knew you were violating the law. The unauthorized use itself is enough.6Oregon State Legislature. Oregon Revised Statutes 537.990 – Criminal Penalties
Penalties escalate in specific situations. Using water illegally at an unlicensed cannabis grow site is a Class A misdemeanor with a maximum fine of $25,000.6Oregon State Legislature. Oregon Revised Statutes 537.990 – Criminal Penalties Oregon has a separate civil penalty framework under ORS 537.992, though the specific fine schedules are set by administrative rule. The practical rule: if water has touched the ground or entered a natural channel, don’t use it without a permit, no matter how small the amount seems. Rain in a barrel off your downspout is a different story, and that’s the water Oregon has expressly left free for you to use.