COVID-19: Many City facilities and all playgrounds are closed. View our City Facilities and Parks Status Map to see what's open.
Get the latest coronavirus updates on our COVID-19 webpage. Para actualizaciones en español, visite nuestra página de Noticias.
PPE Grants Open: Apply for the Hillsboro Protective Equipment Grant for small businesses. Solicite una subvención para pequeñas empresas.

Backflow Prevention and Cross Connection Control Program

Press Enter to show all options, press Tab go to next option

The City of Hillsboro Water Department is responsible for safeguarding the public water system from pollution and contamination. Through operation of the state-mandated Backflow Prevention & Cross Connection Control Program, the Hillsboro Water Department helps protect your drinking water by:

  • Assisting customers with compliance of backflow prevention practices and regulations.
  • Identifying, eliminating, or protecting cross connections.

Backflow & Prevention

What is backflow?
Backflow is the reversal of the normal flow of water.

What causes backflow?
Backflow is caused by pressure differences, including a sudden drop in water pressure in our public system or when a building’s plumbing system has higher pressure than the public water supply. Both situations can allow water and contaminants from a private plumbing system to reverse flow into a home or building’s plumbing system or the public water supply, potentially contaminating the water for other users.

How is backflow prevented? 
Installing a backflow prevention device protects plumbing systems and our public water supply by preventing backflow.

Required Yearly Testing of Backflow Prevention Devices

Image showing a backflow testThe Hillsboro Water Department’s Backflow Prevention & Cross Connection Control Program requires all customers to test their backflow prevention assemblies:

  • After initial installation.
  • After any repair, replacement, or relocation.
  • Each year by a certified backflow assembly tester.

Hillsboro Water Department customers with backflow assemblies required to be tested will receive a yearly reminder letter. Failure to conduct the required yearly backflow prevention assembly test will result in denial or discontinuation of water service.

The following actions should be taken to ensure compliance each year:

  • Contact a State of Oregon approved Certified Backflow Assembly Tester.
  • Schedule a test.
  • Provide your account number to the tester.
    • Your account number is listed on the reminder to test letter you received from the Hillsboro Water Department as well as on your City of Hillsboro Utility Bill.
    • You can request your account number as well by calling 503-681-6163 or sending an e-mail.
    • Your account number gives testers information about the assembly(s) at your location, such as make, model, and serial number. It does not identify you or provide your contact information.
  • Once the test is complete, the certified tester will submit your results to the Hillsboro Water Department through Ecosconnect. The test can also send you a copy of the test report.

Cross Connection

What is a cross connection?
A cross-connection is any temporary or permanent connection between a public water system or consumer’s potable (i.e., drinking) water system and any source or system containing non-potable water or other substances.

What are examples of common cross connections?

  • Hot tubs.
  • Auxiliary water systems (wells).
  • Hoses submerged in polluted or contaminated water.
  • A secondary source of irrigation water (from a well or pond) pumped into an irrigation system directly connected to the drinking water supply system.
  • A heating boiler with treatment chemical added to prevent internal corrosion being connected directly to the water supply for make-up water.
  • An underground lawn sprinkler system directly connected to the water supply system.
  • A fountain or swimming pool directly connected to the water system for filling.  

How are cross connections controlled?
Cross connections can lead to contamination when a change in pressure within the water supply piping allows the water to flow backwards. This reversal of flow, called backflow, can allow contaminated water to flow back into the supply piping, threatening health and safety.

Although under normal circumstances the city water supply is pressurized to keep water flowing to your tap, unforeseen circumstances (such as the need to fight a fire, or when a water main breaks) can suddenly change the pressure in the supply piping, allowing the water to siphon back from your tap to the city supply.

Backflow prevention devices are installed to protect against cross connection contamination caused by backflow conditions.

Questions, Concerns, or Additional Information

Contact the Hillsboro Water Department Backflow Prevention & Cross Connection Control Program at 503-615-6733 or

Frequently Asked Questions

Expand/Contract Questions and Answers

  • Why is it important for water suppliers to prevent backflow?

  • Why do backflow preventers have to be tested each year?

  • I received a letter saying I need to install a backflow preventer. How do I do that?

  • I am a renter. Why did I receive a letter from the Hillsboro Water Department about the backflow preventer?

  • I received a letter to test my a backflow preventer at a home/property I sold previously. How do I update my information?

  • I’m going to be late on having my residential backflow assembly tested. What can I do?

  • What happens if my backflow assembly fails the test?

  • Is there a general compliance schedule and process?

  • Do backflow testers work for the City of Hillsboro?

  • How do I know if I need to install a backflow preventer?

  • What precautions can I take to help keep drinking water safe?

  • A backflow preventer was already installed when I moved into this home/commercial space, but I don’t think I need it. What should I do?

  • I don’t use my irrigation system. Do I still have to test and maintain my backflow preventer?

  • Will installing a backflow prevention assembly affect my water heater?

  • Where can I read more about the City of Hillsboro’s Cross Connection Control Program standards?