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1. What is backflow?

Backflow occurs when water flow is reversed from its intended direction and, by way of a cross connection, is pushed or siphoned back into the drinking water system. Backflow can occur by the following mechanisms:

• Backsiphonage - The pressure in the drinking water system is lowered. This type of backflow can result from water line flushing, fire fighting, or water main breaks.
• Backpressure - The pressure in a customer's piping system is greater than that of the drinking water system. This primarily occurs in commercial applications involving pumps, high rise buildings, or boilers.
• Examples:
  • A garden hose submerged in a bucket of soapy water, hot tub, or swimming pool creates a cross connection. This allows the contaminated water (soapy water or chemically treated hot tub or pool water) to be backsiphoned into the water system.
  • Water containing lawn chemicals is backsiphoned into the water system by way of a lawn irrigation system.

2. How can cross connections and backflow affect my drinking water?

If a cross connection exists and backflow occurs, contaminants can be drawn back through pipes and into the drinking water system. This has the potential to pollute drinking water and create a potential health hazard. Examples:

• A garden hose is submerged in a bucket of soapy water. A water main breaks down the street, lowers water pressure, and soapy water from the bucket is backsiphoned through the hose and into the water system (backflow). At the same time, someone at the residence pours a glass of water from the kitchen faucet. The soapy water flows back out the kitchen faucet, creating a contaminated glass of water.
• A sprinkler head from a lawn irrigation system sits in a puddle of water containing fertilizer (cross connection). Two blocks down the street, firefighters connect to the water system to fight a fire and water pressure is lowered. The puddle of water containing fertilizer is backsiphoned through the sprinkler head and into the water system (backflow.) Meanwhile a neighbor is taking a shower. The fertilizer-contaminated water flows back through the water system and out the neighbor's shower head.

3. What can I do to prevent backflow?

The easiest way to avoid backflow is to eliminate cross connections between the drinking water system and contaminants. Sometimes cross connections cannot be avoided. In these cases, the installation of a backflow prevention device will stop backflow. Examples:

• Avoid creating a cross connection when filling a bucket, hot tub or swimming pool. By leaving a gap between the hose and the water in the container, you eliminate the cross connection and the possibility of backflow.
• Install a backflow prevention device between the lawn irrigation system and the drinking water system to prevent backflow.

4. What is a backflow prevention assembly?

A backflow prevention assembly is a mechanical valve arrangement, which prevents the reversal of water flow, once it has passed through the valve. There are different types of backflow prevention assemblies for different situations and different degrees of hazard.

5. When is a backflow prevention assembly required?

Anytime a connection to the water system is made, the City's Backflow Prevention Division should be contacted to determine backflow prevention requirements. The Backflow Prevention Division is open Monday through Friday, between the hours of 6:30 a.m. and 3 p.m. They can also be reached by calling 254-501-6500, ext. 4. A backflow prevention assembly may be required if you have a:

• Carbonation system
• Chemical feed
• Fire suppression system
• Lawn irrigation system
• Swimming pool or spa
• Water feature such as an ornamental fountain or fish pond

Underground Lawn Sprinklers / Irrigation Systems

The City of Killeen requires all underground lawn sprinkler / irrigation systems to have either a pressure vacuum breaker (PVB) or a reduced pressure zone assembly (RPZ) on all new installations. If there is an old double check in place, it is acceptable as long as it passes the test, once if fails or needs repair, it must be replaced with a PVB-where applicable or an RPZ. City code prohibits any type of cross connection which could endanger the water system.

6. What is a Certified Backflow Assembly Tester and how can I find one?

A Certified Backflow Assembly Tester is someone who has completed a state-approved, 40-hour training course in backflow prevention assembly testing and has passed a proficiency test to prove his/her knowledge. Many plumbing, fire sprinkler, and lawn irrigation companies, as well as backflow prevention testing companies, are listed in local telephone directories and provide testing services in the Killeen area. As a convenience, the City of Killeen maintains a partial list of companies offering the services of Certified Backflow Assembly Testers.

7. What does it cost to test a backflow prevention assembly?

Backflow prevention assembly testing is done by private companies who set their own rates. Testing costs vary, so getting quotes from several companies is recommended.

Texas Commission on Environmental Quality, TCEQ, mandates the City of Killeen establish and maintain a cross connection control program. The City of Killeen Ordinance states the City will terminate water service should a property owner fail to comply with cross connection/backflow regulations. This includes testing and maintenance of backflow prevention assemblies.

8. What are some different types of backflow prevention assemblies, devices, and methods?

Types of Backflow Prevention

• Air Gap (AG): An AG is a physical separation between the end of the discharge pipe and the flood level rim of the container being filled. The separation must be two times the diameter of the opening of the discharge pipe. This is the highest form of protection, since the drinking water supply is physically separated from the container.
• Atmospheric Vacuum Breaker (AVB): An AVB is a non-testable device consisting of an air inlet valve or float check, a check seat and an air inlet port(s). This device is designed to protect against a non-health hazard or a health hazard under a backsiphonage only.
• Double Check Detector Assembly (DCDA): The DCDA is a mechanical valve assembly consisting of two DCVAs, one that is line sized to provide full flow characteristics and one which is smaller (either half or three-quarter inches) located on a detector line. It is used for services having non-health hazards and under conditions of backpressure or backsiphonage, usually for fire suppression systems.
• Double Check Valve Assembly (DCVA): A DCVA is a mechanical valve assembly consisting of two internally loaded, independently operating, check valves together with tightly closing resilient seated shut-off valves upstream and downstream of the check valves. It is used for services having non-health hazards and under conditions of backpressure or backsiphonage, usually for fire suppression systems.
• Pressure Vacuum Breaker (PVB): A PVB is a mechanical valve assembly that includes a check valve, which closes with the aid of a spring when water flow stops. It also has an air inlet valve, which opens when the internal pressure exceeds atmospheric pressure, preventing backsiphonage. It is used for services having either health hazards or non-health hazards and no backpressure conditions; it is typically used on irrigation systems.
• Reduced Pressure Detector Assembly (RPDA): The RPDA is a mechanical valve assembly consisting of two RPs, one that is line sized to provide full flow characteristics and one which is smaller (either half or three-quarter inches) located on a detector line. The RPDA is used on fire suppression systems which pose a health hazard.
• Reduced Pressure Zone Assembly (RP): An RP is a mechanical valve assembly consisting of two internally loaded, independently operating, check valves and a mechanically independent, hydraulically dependent relief valve located between the check valves. It is used for services having either health hazards or non-health hazards and under conditions of backpressure or backsiphonage and gives the highest level of protection among the mechanical backflow prevention assemblies.

9. Do I need a permit to have a backflow prevention assembly installed and is there a permit fee?

Yes, a plumbing permit is required to install a backflow prevention assembly. Permits can be obtained Monday through Friday, between the hours of 8 a.m. and 5 p.m. through the City's Permit Department at:

100 E Avenue C
Killeen, TX 76541

For permit fee information, contact the Permits Department at 254-501-7762.

10. Who can install a backflow prevention assembly?

The property owner, a licensed plumber, or a landscape contractor licensed to install backflow prevention devices. A plumbing permit is required.

11. What does it cost to install a backflow prevention assembly?

Backflow prevention assembly installation is done by private companies who set their own rates. Installation costs vary, so getting quotes from several companies is recommended.

12. Why am I required to have my backflow prevention assembly tested?

Backflow prevention assemblies have internal seals, springs, and moving parts that wear out. Regular testing is required to ensure backflow prevention assemblies are functioning properly and have not been bypassed. A visual check of air gap assemblies is sufficient, while mechanical assemblies must be tested with special equipment.

13. How often do backflow assemblies need to be tested?

All backflow prevention assemblies must be tested at least annually and immediately following any repair, maintenance, or relocation. Assemblies that repeatedly fail may require more frequent testing or replacement.

14. Who is responsible for the testing and maintenance of the backflow prevention assembly?

It is the responsibility of the property owner to ensure the assembly is in good operating condition. A person who is state-certified in backflow assembly testing must perform the test and submit the results to the City of Killeen. If any repair work or maintenance is performed, the assembly must be retested immediately. All test results must be submitted to the City of Killeen. The Certified Tester should mail or bring the original test results to the City at:

City of Killeen
Water and Sanitary Sewer Department - Attention: BPAT&CSI
805 W Jasper
Killeen, TX 76542