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Backflow prevention and cross-connection control

We depend on property owners to protect our community's health by installing backflow prevention assemblies where required. The Oregon Health Authority requires public water systems to have active backflow prevention and cross-connection control programs.

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What is backflow?

Diagram showing how a backflow preventer keeps water flowing in one direction from the public drinking water supply to the private property.
Backflow preventers keep contaminants from flowing back into the drinking water supply.

Backflow occurs when water in a piping system flows opposite of the direction it should. Backflow can be caused by water pressure either pushing or pulling water flow in the opposite direction that it's supposed to go. 

Backflow can be a public health concern when drinking water pipes are connected to other types of piping systems, such as a lawn irrigation system or a fire sprinkler system in a large building, or to other sources of water. When backflow occurs, chemicals, fertilizers, or other types of contaminants or pollutants can be pulled or pushed back into the drinking water system and show up at your or neighbors' taps.

You can simulate backflow when drinking water through a straw: pull water into your mouth and then, instead of swallowing, blow or push the water back through the straw and into the glass. Backflow can occur in the same way, and used or nonpotable water can be pulled or pushed back into the potable water supply.

Fortunately, backflow contamination is preventable by installing and maintaining an approved backflow prevention assembly. To protect you and your neighbors, backflow assemblies are required for many commercial and residential water customers.

Who needs to install an approved backflow prevention assembly?

Property owners must install an approved backflow prevention assembly if there is a risk that backflow could happen on your premises. Even if there is a potential cross-connection risk identified on your property, you may be required to install an approved backflow prevention assembly on your water service.

These installation requirements are from the State of Oregon and the City of Portland. We are responsible for protecting the public water system from backflow through cross-connections.

If you're unsure whether you need to install a backflow prevention assembly, please contact our Backflow Program Coordinator at 503-823-7480.

So, you have a backflow assembly. What are the testing requirements?

You, the property owner, are responsible for installing, testing, and maintaining your backflow prevention assembly. Find out more about testing requirements and submitting test results on our Submitting backflow assembly test reports page.