Backflow and cross connection control

A cross connection is an actual or potential physical connection between our drinking water and anything that could pollute or contaminate the water supply. For example, food and beverage processing equipment without backflow preventers, have the potential for chemicals and/or contaminants to flow back into the system and contaminate the water supply.

Backflow is the undesirable reversal of flow of non-potable water or other contaminants through a cross connection and into the water distribution system. When the flow is reversed or "backflow" occurs, contaminated water can flow backward, drawing a contaminant into the water supply. There are two types of backflow - backpressure and back siphonage.

Backflow is typically caused when an unforeseen change in water pressure allows the water to flow in reverse of the normal direction in the water distribution system, creating the potential for a contamination to a drinking water supply. A drop in pressure could be caused by a variety of circumstances, including a water main break or the need to fight a fire.

• Irrigation or lawn sprinkler equipment
• Food and beverage equipment
• Wash basins and service sinks
• Laboratory equipment
• Fire sprinkler systems
• Chemical feed equipment
• Boilers 
• Radiant Heat

Visit the Backflow Preventer Choices and Requirements page for information on types of backflow preventers and specific applications.

Why an annual test on the backflow prevention assembly?
Backflow prevention assemblies are installed to protect our drinking water from potential sources of contamination. The Washington State Administrative Code requires testing by a certified Backflow Assembly Tester (BAT) to ensure they are functioning as designed.

Who will test my backflow prevention assembly?
The City of Bainbridge Island Public Works, Operations & Maintenance Division will publicly bid a service contract to hire a Washington State Certified Backflow Assembly Tester (BAT) to conduct annual Washington State-required testing for backflow prevention assemblies. The property owner shall be charged the direct cost to test the assembly on the customer’s water bill. (This program does not include repair or replacement of backflow assemblies that do not pass the annual inspection.) 
  
What happens if I do not test my backflow prevention assembly?
To ensure that your backflow prevention assemblies are functioning as designed, it is important to the City's water system to have testing performed annually. Failure to test increases the risk to our water supply should your assembly fail to prevent backflow.  

Failure of the property owner to grant permission to the City hired Washington State Certified Backflow Assembly Tester (BAT) to enter the premise for annual testing in a timely manner will result in the City installing a containment backflow device downstream of the water meter. All costs incurred for non-compliance installations, repairs, and subsequent tests are the responsibility of the property owner and will be assessed on the following month’s water bill. 
  
More Information
For answers to specific cross-connection control questions, please contact the cross connection control specialists at Operations and Maintenance by email or phone (206.842.1212).

• City of Bainbridge Island Municipal Code 13.20
• Washington State Administrative Code WAC 246-290-490
• State Building Code Adoption and Amendment of the Uniform Plumbing Code
• Washington State Department of Health - Cross Connection Control
• USC Foundation for Hydraulic Research and Cross Connection Control
• American Water Works Association
• Washington Certification Services

For answers to specific cross-connection control questions, please contact the cross connection control specialists at Operations and Maintenance by email or phone (206.842.1212).

Sign-up for the City's Notify Me listserv to stay on top of program requirements, changes, testing schedules, etc., and select Backflow Testing.