What is backpressure?

Backpressure is backflow caused by a downstream pressure that is greater than the upstream or supply pressure in a public water system or consumer’s potable water system. Backpressure can result from an increase in downstream pressure, a reduction in the potable water supply pressure, or a combination of both. Increases in downstream pressure can be created by pumps, temperature increases in boilers, etc. Reductions in potable water supply pressure occur whenever the amount of water being used exceeds the amount of water being supplied, such as during water line flushing, fire fighting, or breaks in water mains. Figure 2 shows how a backpressure scenario can occur. 

Diagram  Description automatically generated

Figure 2 – A superior pressure in a nonpotable system (the chemical storage tank) pushes harmful pollutants into the potable water supply when the valve is left open with the compressor on (Image Credit: AWWA)

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