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Backflow Program

Protecting Our Water Supply

Safeguarding the public water system is an essential part of our mission to protect public health. Each connection to the public water system, whether it is a residential home or a commercial business, presents a potential opportunity for contaminants to enter the public water system. To protect against this, Rainbow administers a cross-connection control program across our service area.

The Oregon Health Authority rules OAR 333-061-0070 mandates that water utilities, such as Rainbow, administer a cross-connection control program. This helps keep drinking water free from contaminant exposure.

As part of Rainbow’s program, our Cross-Connection Specialists conduct site inspections to determine if an actual or potential cross-connection hazard exists on a customer’s plumbing system. When conditions related to water service change on a property, such as installing an irrigation system or installing a well with a pump, a backflow assembly is often required. To keep our communal water supply protected, please let Rainbow know of any situation that may require a backflow assembly by calling us at 541-746-1676.


A cross-connection is a point in the drinking water system where a contaminant or non-potable (non-drinking) water can potentially enter the drinking water supply.


Water systems are designed to flow in one direction. However, a drop in pressure or a break in a water line can send water flowing in the opposite direction, drawing contaminants and other chemicals into our water system. This reversal of flow is called backflow, or back-siphoning. Backflow into our public water system can pollute or contaminate the potable (drinking) water making the water unsafe to drink. Rainbow has a responsibility to provide safe drinking water under all foreseeable circumstances.

Without barriers to prevent backflow, contaminated water from private plumbing systems, including industrial plants, pools, and medical facilities, could flow into our public system and impact water quality.

State and federal laws require water utilities to identify all connections to the public supply and have a program in place to prevent backflow. We do this by requiring customers whose water use presents a backflow hazard to install a backflow prevention assembly and have it tested annually.

Backflow Prevention Assembly

Backflow assemblies prevent contaminated water from re-entering Rainbow’s drinking water supply in the event of a malfunction in a consumer’s pressure equipment or a sudden drop in pressure in Rainbow’s water system.

Our Cross-Connection Control Program

As Rainbow administers our backflow prevention program, actions may include:

  • Determining whether a customer must install a backflow prevention assembly and if so, which type
  • Developing and maintaining standards and installation requirements for installing backflow assemblies
  • Inspecting newly installed backflow assemblies
  • Maintaining records of all customer backflow assemblies in our service area and documenting annual backflow test results for each
  • Maintaining a list of certified backflow testers to provide as a resource for customers to call to have their assembly tested

Backflow assemblies are part of a customer’s private plumbing system. Customers are responsible for having their backflow assembly(s) installed according to our installation requirements and tested by a certified tester at the time of installation (at least annually, after repairs or relocation, and/or after a backflow incident) with the passing test results submitted to Rainbow within 14 days.

Our Cross-Connection Specialists will make every effort to work with you to facilitate the installation and testing of the appropriate assembly if needed.

Remember, these requirements are in place to protect the community’s water supply, as well as the water quality in your home.

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