Cross Connection Control

The purpose of the Cross-Connection Control and Backflow Prevention Program is to safeguard public drinking water and protect the health and safety of our customers from contamination by isolating any potential cross-connections which could backflow into the public water supply. It is the responsibility of both CLWSC and its customers to protect the public water supply, by adhering to the rules and regulations set forth by the Texas Commission on Environmental Quality (TCEQ).


Customer Service Inspections

Backflow Prevention


Additional Information

Frequently Asked Questions

Cross-Connection Control & Backflow Prevention Manual 




Customer Service Inspections

Customer Service Inspections are performed to make sure there are no direct connections between the public water supply and a potential source of contamination or private water system that are not protected by either an air gap or an appropriate backflow prevention assembly.

For the convenience CLWSC customers, a list of local CSI inspectors and a CSI certificate is available. The inspection certificate shall be provided to CLWSC within 10 business days of the inspection.




Backflow Prevention

To protect the water system, backflow prevention assemblies are required for all connections that may present a potential source of contamination of the public water system. Backflow prevention assemblies must be tested upon installation and annually thereafter.

For the convenience of CLWSC customers, a list of local Backflow Prevention Assembly Testers (BPAT) and a Test and Maintenance Report is available. The T&M Report shall be provided to CLWSC within 10 business days of the test.





If a customer fails to comply with TCEQ rules and regulations and adhere to CLWSC Cross-Connection Control and Backflow Prevention Program, CLWSC shall, at its option, terminate service in order to protect the public water supply. Any expenses associated with this enforcement shall be billed to the customer.

For further information please contact CLWSC or email questions to




Additional Information

CLWSC’s Cross-Connection Control and Backflow Prevention Manual covers definitions, responsibilities, procedures, and enforcement as it relates to Customer Service Inspections and Backflow Prevention. All Backflow Prevention Assemblies shall be installed in accordance with CLWSC Standard Details

In order to ensure that the backflow prevention assembly is in accordance with TCEQ regulations, you should refer to the Assessment of Hazards and Selection of Assemblies in the Manual or contact CLWSC.





Frequently Asked Questions

Why does CLWSC need a Cross Connection Control and Backflow Prevention Program?

The program safeguards the public drinking water and protects the health of its customers by ensuring that any contaminants that could backflow into the public water supply system are isolated within the customer's internal distribution system.

What is a Cross-Connection?

Cross-connections are the physical links that allow backflow to occur. Through physical connections, contaminations of the water supply are possible as a result of backpressure or backsiphonage. Cross-connections are so common that they may go unnoticed and unrecognized. Recognition of common cross-connections is important to eliminate the potential for contamination to the public water supply.

What is a Customer Service Inspection (CSI)?

Inspectors will check to make sure there are no direct connections between the public drinking water supply and a potential source of contamination or private water system that are not protected by either an air gap or an appropriate backflow prevention assembly in accordance with TCEQ regulations. They will also ensure that no pipe or pipe fitting which contains more than 8% lead or solder which contains more than 0.2% lead exists.

When should a Customer Service Inspection (CSI) be performed?

CSI’s are performed on new construction, existing services where contaminant hazards are suspected and existing serviced where major renovations or expansion of the distribution facilities have occurred.

What is Backflow?

Backflow is any undesirable or unwanted reversal flow of used or non-potable water or substance from any domestic, industrial or institutional piping system into the potable water distribution system.

What is Backsiphonage?

Backsiphonage is the reverse pressure gradient due to a loss of pressure in the supply lines, caused by main line breaks, use of fire hydrants and other variables. The loss of pressure in the supply lines can cause water and other contaminants in the customer’s lines to be “sucked” back into the public water supply, similar to drinking out of a straw.

What is Backpressure?

Backpressure is the flow from a customer’s higher pressure system through an unprotected cross-connection. Many forces can create backpressure including centrifugal and positive displacement pumps, water at a higher elevation, water in pressurized vessels, boilers or steam systems, heating or freezing water in closed fluid-filled pipes or containers.

How do you prevent backflow?

The two main ways to prevent backflow is to install a backflow prevention assembly or create an air gap.

What is an air gap?

An air gap is a physical separation of the public water supply from the source of the contamination. The air gap is provided by an unobstructed vertical separation of two times the diameter of the water supply outlet’s effective opening (but never less than one inch) between the discharge end of the water supply pipe and the flood level rim of the receptacle. Screened protection over the water supply outlet is recommended to protect the water supply pipe from insects and vermin. Caution must also be exercised if the tank receptacle contains substances which may emit toxic fumes or vapors which could be backsiphoned into the fresh water supply line.

What is a backflow prevention assembly?

The basic mechanism for preventing backflow is a mechanical backflow preventer, which provides a physical barrier to backflow.

How do you protect a backflow prevention assembly?

Some backflow prevention assemblies are below ground while others are above ground; in either instance it is important to properly insulate your device to protect them from freezing. You may refer to Freezing Temperatures for more information on how to protect outdoor fixtures.

You can also purchase insulated bags and/or insulated/decorative rocks to protect and conceal above ground devices.


Why do backflow prevention assemblies need to be tested?

Mechanical backflow prevention assemblies have internal seals, springs, and moving parts that are subject to fouling, wear or fatigue. Also, mechanical backflow preventers and air gaps can be bypassed. Therefore, all backflow prevention assemblies have to be tested periodically to ensure that they are functioning correctly.

How often does the backflow prevention assembly need to be tested?

In order to insure the proper operation of a backflow prevention assembly, it must be tested and certified upon installation and at least once a year thereafter by a licensed backflow tester