The purpose of the District's Cross-Connection Program to secure and protect the public water supply from potential sources of contamination and optimizing water quality through identifying and eliminating potential cross-connections.

Backflow prevention is the most significant aspect of the cross-connection program, directed at preventing any introduction of harmful substances to the distribution system. Typically, a backflow prevention assembly (BPA) device is installed at the water meter, consistent with District standards, to protect the public water supply.

TCWD requires all BPAs in its service area to be tested annually, and provides this service at a nominal charge.  The backflow test report form can be found below as well as resources and information on backflow assemblies. 

In 2025, TCWD prepared an updated Cross-Connection Control Management Plan (CCCMP) consistent with the State Water Resources Control Board (SWRCB) Cross-Connection Control Policy Handbook (CCCPH) adopted in 2024.

On June 18, 2025, the TCWD Board of Directors approved the final plan and adopted an ordinance consistent with SWRCB requirements; the final CCCMP is available here. For more information about TCWD's CCCMP, please contact staff at (949) 858-0277 or customerservice@tcwd.ca.gov.

What is backflow?

Backflow is water flowing in the opposite direction from its normal flow. TCWD's potable water system is designed to keep the water flowing to you. When hydraulic conditions within any water system deviate from "normal," the direction of water flow can be reversed. This creates a backflow condition and the potential for contaminated water entering the potable water distribution system.

How does backflow occur? 

Backsiphonage can occur when there is a sudden reduction in the water pressure of the distribution system, such as during fire fighting or when a water main breaks. At these occurrences, water flow can be reversed. This reversal can create a suction effect and draw potential contaminants into the potable (drinking) water system.

Backpressure is created when pressure in a water system exceeds the pressure in the potable system providing the make-up water. This can force the potable water to reverse its direction of flow through the cross-connection between the two systems. Potential contaminants can then enter the potable water system.

How can backflow be prevented? 

• Be aware of and eliminate cross-connections.
• Maintain air gaps. Do not submerge hoses or place them where they could become submerged.
• Use hose bibb vacuum breakers on fixtures (hose connections in the basement, laundry room and outside).
• Install approved, testable backflow prevention assemblies on lawn irrigation systems.
• Install an approved, testable backflow prevention assembly at your home's water service connection.
• Do not create a connection between an auxiliary water system (well, cistern, body of water) and the water supply plumbing.

What is a Backflow Prevention Assembly (BPA)? 

A backflow prevention assembly is an approved, testable assembly which uses check valves and/or relief valves, in different configurations, to prevent potential contaminants for flowing into the potable (drinking) water system.

An approved backflow prevention assembly has gone through an approval process at the Foundation for Hydraulic Research and Cross-Connection Control at the University of Southern California. This is a two-step process of laboratory tests and a 12-month field test. Only assemblies successfully completing the entire testing procedure are recognized by TCWD as approved backflow prevention assemblies.

Who is required to have a BPA?

TCWD's General Policy (Chapter 3, Section 3.5), as well as Federal and State law, requires that water suppliers protect their water systems from contamination. When a determination is made by TCWD that the potable (drinking) water distribution system may be subject to contamination through a backflow condition, the customer will be notified and required to install an approved backflow prevention assembly. TCWD makes these decisions based on a case-by-case basis. Residential, commercial, and irrigation customers demonstrating a high potential for contaminants to enter the potable water system must install and maintain backflow prevention assemblies.

Forms & Links
TCWD BPA Test & Maintenance Report Form
USC Foundation for Cross-Connection Control & Hydraulic Research
Orange County Environmental Health Services - Cross Connection
American Backflow Prevention Association

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