RP Testing and Maintenance


RP (Reduced pressure principle backflow preventer); is the highest level of protection by mechanical means, for protection from backflow. May also be called an RPZ or reduced pressure zone assembly.

*This article is only meant as a summary of the testing procedure, you are responsible to test backflow preventers to the standard of your authority having jurisdiction.

Watts 909 series RP Reduced pressure backflow preventer

RP Testing Steps

  1. Relief valve - The relive valve must open and dump water at a pressure higher than 2 PSI.
  2. Check valve #2 - Check valve #2 must close tight in the reverse direction of flow and must hold a differential pressure for 2 min.
  3. Check valve #1 - Check valve #1 must close tight in the direction of flow and maintain a pressure of at least 3 PSI for 2 min.
  4. Static line pressure - Record the static water pressure at test cock #1.




RP Maintenance Hints

  • Always use the manufacturer's parts.
  • Check valve #1 and #2 are not always interchangeable, even if they look the same.
  • Always bleed the test cocks to remove dirt before attaching your gauges.
  • Larger devices may have springs under pressure; caution should be taken when performing maintenance.
  • Clean in-line strainers
  • If the RP is constantly dumping water; close shut off #2, if it continues check valve #1 is likely leaking.
  • If removing a backflow device from service place an electrical jumper across the pipe opening first.