What Is Backflow?

Backflow is the unintended reversal of water flow in a drinking water (potable) distribution system. Under normal conditions, water flows in only one direction. However, if water pressure drops significantly, such as during a water main break or periods of high demand, water can flow backward into the public water system. This type of backflow is called backsiphonage.

Backflow can also occur due to back pressure, which happens when pressure from a connected system (such as a boiler, pump, or elevated piping) becomes greater than the pressure in the public water system, forcing water to flow in the wrong direction.

Common Risks
Backflow can occur in everyday situations. For example, if a garden hose is submerged in a hot tub or swimming pool, or connected to a fertilizer or chemical sprayer, contaminated water can be siphoned back into the drinking water supply if pressure drops.

Prevention
Backflow prevention devices are designed to stop contaminated water from flowing backward into the public water system, helping protect the safety and quality of our community’s drinking water. Backflow prevention assemblies are required to be tested at installation and at least once per year thereafter by a licensed and City-registered tester.

Who Needs a Backflow Prevention Assembly?

• Irrigation systems
• Fire sprinkler systems
• Commercial and industrial facilities
• Multi-family properties
• Properties with boilers, chemical systems, or auxiliary water supplies
• Any connection deemed a potential cross-connection hazard

Backflow Testers 

Only testers who are licensed by the State of Texas and registered with the City of Lewisville are authorized to test backflow prevention assemblies.

Backflow Tester List

The Backflow Tester List is an up-to-date listing of all backflow testers currently registered with the City of Lewisville. The City does not endorse or recommend specific testers.

**NOTE: Not all testers are licensed to test all types of backflow assemblies. Please refer to the last column of the report to determine if the backflow tester you select is licensed to test the device(s) at your home or business.**

Informational Links

• American Backflow Prevention Association (ABPA)
• Texas Commission on Environmental Quality (TCEQ)

Frequently Asked Questions