Backflow Assemblies
Overview
Cross-Connection -- also known as backflow -- means any actual or potential physical connection between a public water system or the consumer's water system and any source of non-potable water supply by backflow. This can include water from common sources including: swimming pools, hot water heaters, and soda fountains.
How does backflow occur?
Backflow occurs when water pressure on the consumer's side of the service connection is greater than the pressure provided by the public water system.
A drop in pressure, also known as back-siphonage, causes non-potable water to get sucked in to the public clean drinking water supply.
Although this is uncommon, the results can be deadly.
How do you prevent backflow / cross-connection contamination?
Backflow prevention assemblies protect the drinking water supply from becoming contaminated. These assemblies are tested annually to ensure they are in proper working order.
Through the Safe Drinking Water Act, a Cross Connection Control Program is required by the Washington State Department of Health and the Environmental Protection Agency to protect the public from contaminated water. This program calls for site inspections to identify and eliminate cross connections as well as annual testing of backflow prevention assemblies.
Legal Requirements for Water Customers / Property Owners / Testers
Annual Testing
Customers must obtain annual inspections and tests of their backflow assemblies to ensure proper functionality. The yearly test will identify any problems so they can be corrected. Please have the completed reports submitted by September 1st of each year. Reminder letters are mailed once a year in June for the devices that are due to be tested.
Certified Backflow Assembly Testers
Any state certified Backflow Assembly Tester (BAT) is able to perform this test. A list of certified testers is available on the Washington State Department of Health o Green River Certification Services web pages.
If you wish to hire an individual whose name does not appear on this list, contact the Washington State Department of Health at 800-525-2536 to confirm their certification.
The City of Duvall does not possess information on costs of service for backflow assemblies. The most accurate way to obtain a current cost estimate is to call Backflow Assembly Testers and compare costs.
Reference
Cross-Connection Control Program (PDF)
Questions
Please call at 425-788-3434 or email us 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.
-
Pressure Reducing Valve (PRV)
-
Reduced Pressure Backflow Assembly (RPBA)
-
Atmospheric Vacuum Breaker (AVB)
-
Double Check Device Assembly (DCDA)
-
Double Check Valve Assembly (DCVA)
Types of Devices
The most common types of backflow device are:
- Double Check Valve Assembly (DCVA)
- Reduced Pressure Backflow Assembly (RPBA)
- Atmospheric Vacuum Breaker (AVB)
- Double Check Device Assembly (DCDA)
- Pressure Reducing Valve (PRV)
Definitions
Cross Connection: a physical connection between drinkable water and a liquid or gas that could make the water unsafe to drink (wherever there is a cross connection, there is a potential threat to public health from the liquid or gas contaminants).
Backflow: water flowing in the opposite of its intended direction, either from a loss of pressure in the supply lines or an increase in pressure on the customer’s side (in either of these situations, if any affected customer’s pipes include a cross connection, contaminants could be drawn through the cross connection into that customer’s pipes—and, if the backflow continues, perhaps even into the water mains).