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The City of Portland, Oregon

Portland Water Bureau

From forest to faucet, we deliver the best drinking water in the world.

Customer Service: 503-823-7770


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Backflow Prevention

Almost one-quarter of Oregon’s population depends on the Portland Water Bureau for safe drinking water. Protecting water safety and quality, public health, and the environment through source water protection, water treatment and distribution, and system maintenance and construction is dependent on the partnership between the bureau, private property owners, residents, and businesses.

The Portland Water Bureau is committed to delivering safe water into our system of storage reservoirs and tanks, and into area pipe systems.

Portland Water System Graphic

Once water is flowing through area pipe systems, the Water Bureau depends on our partnership with private property owners, residents, and businesses to keep water safe. Where each home, building, and business is connected to an area supply pipe (water main), cross connection is created. Each cross connection has the potential to introduce contaminates into the water supply, if it is not protected by a backflow prevention assembly.

Propery connection graphic

A backflow prevention assembly is a valve that allows water to flow in only one direction. In the event pressure in thBackflow prevention assemblye city distribution system drops or the property side pressure increases significantly, an approved, properly functioning backflow prevention assembly will not allow the private plumbing contents to flow back into the public water system. 


Ensuring public health through a safe and reliable water system is accomplished, in part, through state health and municipal codes across the country. In Oregon the Oregon Revised Statues (Chapter 333 Division 61-0070); Oregon Health Authority Rules, (Chapter 333-061-0070, Table 42); and City of Portland Water Code, (Title 21, 21.12.320), require property owners to install an approved backflow prevention assembly and housing on water services where warranted.