Backflow Prevention Assemblies

Backflow Overview

A backflow prevention assembly, or “backflow assembly,” for short, is a mechanical device incorporated into your plumbing system with one-way valves that prevent potential contaminants from reversing flow (backflow) and entering the drinking water system of a dwelling or the City water supply. They are most associated with fire sprinkler and irrigation systems.

Types of Devices

The most common types of backflow assemblies are:

  • Double Check Valve Assembly (DCVA)
  • Reduced Pressure Backflow Assembly (RPBA)
  • Atmospheric Vacuum Breaker (AVB)
  • Double Check Detector Assembly (DCDA)

Test Your Backflow System Annually

Annual testing of your backflow system is required by Washington State Code WAC 246-290-490, to assure that it is in perfect working order. The annual test is conducted by a state certified Backflow Assembly Tester (BAT) of your choosing and will identify any problems so they can be corrected. Your Tester will enter the test results using the City of Issaquah Backflow Test Report Entry Portal. BATs should send an email to register.

Each property within the City of Issaquah, that contains a backflow assembly, is assigned an account number and a yearly due date for inspection of that assembly. Reminder letters are mailed each month for the assemblies that are due to be tested, along with detailed account information to provide to your tester.

If an annual test is not performed, we will be required to terminate the water service to the address as authorized by Issaquah Municipal Code 13.13 and WAC 246-290-490. Water service will only be restored when the backflow assembly is in compliance with City of Issaquah and Washington State codes.

Failed Backflow Tests

If your backflow assembly fails the test, repairs must be performed immediately, and then retested. A backflow assembly that has failed will not protect your, nor our water supply. Your tester will be able to assist you with this issue. Your account cannot be considered current until the City receives passing test results for each backflow assembly.

Certified Backflow Assembly Testers

Any Washington State certified Backflow Assembly Tester (BAT) can perform this test. The City of Issaquah maintains a list of local certified testers as a convenience to our customers. These testers have requested that their company names appear on our current list. This list does not include all certified BATs and is not a recommendation to hire. A copy of this list is included with the yearly mailing of your account information, test forms and due date. For a full list of state certified BATs, go to the Washington Certification Services website.

Tokay WebTest Online Test Report Entry Transition

Since Jan. 1, 2023, all backflow test report submissions are completed in the Tokay WebTest online platform. Completed test reports will no longer be received via mail, fax, or email. BATs will need to email to register for the Tokay WebTest online portal and receive their access information before they are able to enter any completed tests.

Cost of Backflow System Test

The City of Issaquah does not possess information on costs of service for backflow assembly testing. The most accurate way to obtain a current cost estimate for a testing fee, is to call BATs and compare costs.


Please call us at 425-837-3470 or email to discuss any problems or concerns that you have with testing or the testing schedule. We are happy to work with you to resolve any difficulties.