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, the Uniform Statewide Building Code and any additional instructions offered by the Public Utility Division. RPP devices are installed in a horizontal position with the relief port down. They should not be installed in a pit or in any location that could experience flooding, as their functionality is impacted by submersion in fluids. To allow for easy access and maintenance, RPP devices should be installed at least 12 inches above the floor with 24-inch clearance on all sides, and should be in a location safe from freezing temperatures and vandalism. The leaking action of the relief valve should also be considered (installation above a floor drain is ideal). 

Unlike RPPs, DCVAs can be installed in a pit and can be submerged but must still be protected against freezing and vandalism. Like the RPP, it should be installed horizontally and in an area that is easily accessible and with plenty of clearance for the maintenance professional to inspect and test the device.

A PVB should be installed in an easily accessible area that is at least twelve inches above the highest downstream outlet (this is necessary thanks to the PVB’s vulnerability to backpressure), and like the other devices must be protected from freezing and vandalism. The air-inlet port must never be blocked or sealed as this defeats the usefulness of the device. 


Finally, Atmospheric Vacuum Breakers (AVBs) must be installed 6 inches above the highest point of downstream outlet, the highest point of downstream usage, the highest downstream piping, and the highest flood elevation. AVBs must be installed downstream of all valves and pumps (aspirators can be used downstream of AVBs). Like all other devices, the AVB must be kept safe from freezing temperatures and vandals, and like the PVB the assembly’s air inlet port should never be blocked or sealed. Figures 4, 5, 6, and 7 display the optimal placement of the various backflow prevention assemblies.

Diagram, engineering drawing  Description automatically generated      Diagram, engineering drawing  Description automatically generated

Figure 4 – RPP placement guide (all images from AWWA)            Figure 5 – DCVA placement guide

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Figure 6 – AVB placement guide                                                                      Figure 7 – PVB Placement guide

Show All Answers

1. Why does the City of Petersburg Public Utilities Division have a Backflow Prevention & Cross Connection Control Program?
2. What is a cross-connection?
3. What is backflow?
4. What is backpressure?
5. What is backsiphonage?
6. Why is backflow a concern to the public?
7. Are all residential homes required to have backflow assemblies?
8. Why are irrigation systems considered to be hazardous to the water system?
9. What type of backflow prevention assemblies are allowed in irrigation systems?
10. How do I know if I have a backflow prevention assembly?
11. What kind of buildings need backflow prevention assemblies?
12. Is there a minimum height that the backflow assembly must be installed?
13. When is a plumbing permit required?
14. Can a backflow device be removed?
15. How frequently does a backflow prevention assembly have to be tested?
16. How much will the inspections/maintenance cost?
17. What credentials are required to inspect and test a backflow prevention assembly?
18. Will I receive notification when to perform my test?
19. What if I don’t receive a letter?
20. What can I do with my test report?
21. Abbreviations