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Avoid Emergency Shutdowns due to Plugged Sensing Lines

January 2, 2018

The sensing lines on older model 2.5” and larger RPBA’s used on high demand systems and buildings are prone to plug. Modern assemblies have a modified bulkhead design which has proven to reduce the likelihood of a plugged sensing line by keeping the water inlet for the sensing line out of the area where high velocity turbulent water is present. There are many buildings which do not have a bypass assembly on the domestic water line which means when you do a temporary shutdown to test the RPBA you may find yourself in an extended shut down with an emergency repair on your plate.Watts 909There is a way to find out whether you have a plugged sensing line or a defective relief valve without causing panic for your customer and their tenants. I do this method any time I work with an older assembly on a building with no bypass. Once I have determined the sensing line is not plugged I will restart the test using the USC method. If I find the sensing line is plugged I will contact the building engineer and we will schedule a calm and peaceful extended shut down on our terms rather than an emergency basis.

  1. Open TC#4, TC #3, LEAVE TC #2 CLOSED, Open and Close TC #1, Close TC #3, Then TC #4. “DO NOT TOUCH TEST COCK #2”
  2. Connect your High side hose to TC #1
  3. Connect your Low side hose to TC #3
  4. Follow USC testing procedures to get your Relief Valve opening point.
  5. If the relief valve does open, restart your test from the beginning using USC test procedures and note you exercised the relief valve on your test report. Be sure and to thoroughly flush TC #2.
  6. IF THE RELIEF VALVE DOES NOT OPEN, CLOSE ALL TEST COCKS AND RESTORE SERVICE. Contact the customer and let them know the assembly has a plugged sensing line and or a defective relief valve that will require attention and an extended shut down before the assembly can be properly tested.
  7. It’s very important to get this repaired ASAP. I usually repair them while I’m at the building but the customer always appreciates being able to have time to let all the tenants know in advance that they will be without water while the repairs are being made.
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