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Backflow FAQ Assemblies

Why is a Reduced Pressure Backflow Assembly (RPBA) required on my irrigation system?

Irrigation systems include but are not limited to agricultural, residential, and commercial applications. SUB Water Division Cross-Connection Control Program Manual and the International Association of Plumbing and Mechanical Operators (IAPMO) classifies lawn sprinkler systems and irrigation systems as a high hazard for several reasons: sprinklers, bubbler outlets, emitters, and other equipment are exposed to substances such as fertilizers, fecal material from pets or other animals, pesticides, or other chemical and biological contaminants. Sprinklers may remain submerged underwater after use or storms. Should the water system pressure suddenly decrease, such as in the case of a water main break, or during a major fire involving multiple fire hydrants, these harmful substances can be back-siphoned into the water distribution system? They may be subject to various on-site conditions such as additional water supplies, chemical injection, booster pumps, and elevation changes. All of these conditions must be considered when determining backflow protection.

Is a Reduced Pressure Backflow Assembly (RPBA) the only assembly I can install on my irrigation system?

Yes, RPBA provides the best backflow protection against the high hazards of an irrigation system. The RPBA provides a warning sign when the assembly is failing and does not allow backflow to occur. A Double Check Valve Assembly (DCVA) is not allowed for new installation because it has no exterior indication of failure, which can be as high as 15%. This means a DCVA could have passed a test but started to fail soon after, a problem that would not be caught until the next annual test, leaving customers unknowingly without protection.

Pressure Vacuum Breaker (PVB) is testable, but proper operation requires the assembly and sprinkler heads to be installed at a certain height and the assembly must also pass testing. Even if the test for the PVB was good, the assembly’s operation may be compromised because of improper installation. A correctly installed RPBA is required instead of the PVB since the installation of the sprinkler heads downstream of the RPBA does not affect the assembly’s operation.

Atmospheric Vacuum Breakers (AVB) are non-testable devices that also require certain installation requirements for the device and sprinkler system. There is no test to determine if this device is working properly and the operation of the device may be compromised by modifications to the sprinkler system. A properly installed RPBA is required instead of the AVB since modifications of the sprinkler system downstream of the RPBA do not affect the assembly’s operation and the RPBA can be tested to verify proper operation.

Why is my backflow assembly installed above ground?

Existing Double Check Valve Assemblies (DCVAs) are installed above ground because in an underground installation the assembly is likely to become submerged in water during the winter months. If the assembly does get submerged underwater the manufacturer’s warranty is void. Also, above-ground installation of DCVAs is recommended by the Foundation for Cross-Connection Control and the Hydraulic Research University of Southern California, because a cross-connection between the test cocks and the water submerging the assembly is created.

Reduced Pressure Backflow Assemblies (RPBAs) are installed 12 inches above ground because this assembly dumps water when the assembly fails. Adequate drainage is needed to ensure discharging water does not back up and flood the assembly.

Are any other backflow assemblies required for residential homes?

All outdoor faucets and hose bibs that have threaded connections where a garden hose can be attached should have backflow prevention protection. This may be in the form of a frost-proof automatic draining outdoor faucet with a built-in backflow preventer or by the use of a screw-on hose bibb vacuum breaker (HBVB) that can be purchased at local hardware or home supply stores.

Note: Customers should take necessary actions to ensure that their backflow prevention assembly or plumbing does not get damaged during freezing temperatures.

How much does it cost to have a backflow assembly installed?

Since there are so many variables, such as pipe size, pipe type, location of installation, backflow assembly size and type, availability of a drain, and the plumber’s individual pricing, the SUB Water Division cannot provide an estimate of the installation cost. However, it is advised that you get at least three quotes so that you can compare installation costs.

How do I know if I have a backflow assembly?

Generally, the backflow prevention assembly is located as close as possible to the water service connection but must remain on private property. It is usually installed outdoors and in a “loop” of the irrigation system that extends above the ground and sometimes near the sprinkler system timer.

Is there a minimum height that the backflow assembly must be installed?

Yes, backflow prevention assemblies should be installed in accordance with the manufacturer’s installation instructions and the Water Division installation requirements. Regulations regarding flow orientation and proper access to the backflow assembly should also be followed.

A plumbing permit is required for the installation of a new backflow assembly or relocation of an existing assembly. Please contact the City of Springfield to obtain the permit.

What is the difference between a backflow device and a backflow assembly, and why are assemblies required?

Backflow devices are installed at a building’s taps and are not testable. Backflow assemblies are installed at a building’s water service connection and are testable and repairable, which is why they are required. Examples of backflow assemblies include a Reduced Pressure Backflow Assembly and a Dual Check Valve Assembly. Examples of a backflow device are a hose-bibb vacuum breaker, atmospheric vacuum breaker, or dual check with atmospheric vent.