Contamination Risk
Fertilizer, chemicals, bacteria, or other contaminants can be pulled into a potable water system through an unprotected connection.
Why Annual Testing Is Required
Backflow
When Water Flows the Wrong Way
Backflow is the unwanted reversal of water through a plumbing system. When pressure changes, water can be pulled or pushed backward, creating a risk that contaminants can enter the drinking water system.
Backflow prevention assemblies help protect public health by preventing contaminated water from flowing back into the drinking water system.
Why It Matters
Why Backflow is a Health Hazard
A cross-connection can allow contaminated water to enter the drinking water system. Backflow prevention assemblies are designed to protect the public water supply by keeping those systems separate.
Hidden Danger
Backflow usually happens because of changing water pressure and often occurs without visible warning. Water may appear clean while it is contaminated.
Protecting Public Health
Backflow prevention assemblies are an important safeguard for protecting public health. Annual testing helps verify that the assembly works properly.
The Science
How Does Backflow Occur?
Backflow occurs whenever water flows in the opposite direction of its intended path due to a pressure differential within the water system. There are two hydraulic conditions that can cause backflow: backsiphonage and backpressure.
Back-siphonage
Backsiphonage occurs when the pressure in the public water system drops below the pressure at a cross-connection, creating a siphon that can draw non-potable water back into the drinking water system.
Back-pressure
Backpressure occurs when pressure on the customer's side of the water system becomes greater than the pressure in the public water supply, forcing water to flow in the opposite direction.
Flow Direction Protected Supply
Normal Flow
Potable water flows from the public water system to the customer's plumbing system.
Pressure Differential
A change in pressure creates the potential for reverse flow through a cross-connection.
Backflow Prevention
A properly functioning backflow prevention assembly prevents reverse flow and protects the drinking water supply.
Stay Compliant
Why Annual Testing is Required
Washington State regulations and local water district requirements call for annual testing of many backflow prevention assemblies. Annual testing verifies that the assembly is operating properly and will protect the drinking water system if a backflow event occurs.
- Required by Washington State regulations
- Required by local water purveyors
- Helps protect the public drinking water supply
- Keeps your property in compliance
