Backflow Prevention

What is Backflow?

Backflow prevention deviceBackflow is a loss of pressure in the public water system that can draw water on customer property (from within fire sprinkler systems, irrigation systems, hot tubs, etc.) back into the public water system. This water can contain contaminants that would put the public water supply at risk. Studies have shown links between waterborne disease outbreaks and the backflow of contaminants from private property. It is critically important to prevent backflow to protect public health.

What Am I Responsible for?

Per OMC 13.04.110, property and business owners are required to install and maintain backflow prevention assemblies where they are needed. Water utility customers are also responsible to have their backflow assemblies tested annually by a State Certified Tester.

A backflow prevention assembly is a device that is installed on a customer's property to prevent contamination from entering the potable water supply. There are four types of devices:

  • Reduced Pressure Backflow Assembly
  • Double Check Valve Assembly
  • Pressure Vacuum Breaker
  • Spill Resistant Pressure Type Vacuum Breaker

Where is a backflow assembly required?
A backflow assembly is required wherever there is a possibility of a cross contamination between the public water system and a non-potable water source. Examples include, but are not limited to, irrigation systems, drainage systems, hot tubs, and other water-using equipment.

Find a Certified Tester

Visit this Washington Certification Services webpage for a list of Certified Backflow Assembly Testers (BAT) by County.

Information for Testers

Download our Backflow Assembly Testing Packet for our standardized testing report form, requirements and instructions on how to submit.

Need a permit? Contact the Community Planning and Development at 360.753.8314.

A Warning About Outdoor Faucets

Everyday things you do when using an outdoor faucet can put you and your family at risk. If an outdoor faucet is in contact (directly or via a hose) with dirty water and there is an unexpected change in pressure, that water can be sucked back into your home's drinking water pipes.

The easiest and best way to protect your family is to install vacuum breakers on all outdoor faucets. Vacuum breakers completely prevent backflow through outdoor faucets and are available at all major home improvement stores for around five dollars.

If you choose not to install vacuum breakers make sure you:

  • Never submerge a hose in a bucket of water
  • Hold hoses above the water line when filling hot tubs, pools, etc.
  • Do not use fertilizer sprayers


Call 360.753.8161 or email

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