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New Pressure Reducing Valve Problem

nibsnibs Posts: 383Member
edited September 2019 in THE MAIN WALL
Brand new Watts PRV works, goes to required pressure (50#) then slowly raises to 70# + which opens the relieve valve. It would seem that this is a classic sign of crud caught in the diaphragm, my bad for not flushing the new house supply line. Any tips on washing the crud out, have tried tapping it while flushing the toilet. Gonna try zero-ing the house pressure, turning the valve up to its highest, and with a faucet open open the supply line for max flushing.

Will monitor pressure closely while doing this.

Really don't want to field strip the prv so any hints would be appreciated.


  • STEVEusaPASTEVEusaPA Posts: 3,691Member
    Is this on a water heater? Then it should be a T&P (temperature & pressure) relief valve.
    First I'd make sure it is the correct one and wasn't installed backwards, which I've seen twice on a boiler.
    Then I'd confirm temperature and pressure with separate gauges.
    You could put a bucket under the relief valve pipe and carefully open the valve to flush it, then let it seat and give it a tap.
    70# seems low for opening on pressure, what's the water temp?

    Also you may need a domestic expansion tank set for the same pressure as your water service.

    Hopefully this isn't on a regular domestic/residential boiler, in which case that's a dangerous pressure.
  • JUGHNEJUGHNE Posts: 6,441Member
    Is this a PRV...pressure reducing valve for filling boilers or
    Pop off valve.....pressure relief valve on a boiler or water heater??
    What is it installed on?

    Your header states relief valve but the text implies a fill valve.
  • nibsnibs Posts: 383Member
    Argh my bad, the problem is with the Pressure reducing valve, not the relief valve. PRV set to 50lbs and pressure relief valve opens at 70 lbs because the prv is going overpressure.
    SORRY (going out to eat worms now)
  • STEVEusaPASTEVEusaPA Posts: 3,691Member
    Oh geez, that's different...good eye @JUGHNE
  • JUGHNEJUGHNE Posts: 6,441Member
    Big boiler....tall building....high city pressure?
    Is the PRV rated to deliver 50PSI?
  • nibsnibs Posts: 383Member
    @JUGHNE ;
    City water 100psi +/-, PRV max input 400# output range 20#to 75#. House is on grade, prv goes to setpoint, then creeps up to 70# plus, & pops off the relief valve.
  • nibsnibs Posts: 383Member
    Should add expansion tank set to 50#
  • STEVEusaPASTEVEusaPA Posts: 3,691Member
    I'm still confused. Is this on a water heater?
  • nibsnibs Posts: 383Member
    Line comes into house, PRV then filter then goes to house for domestic use, Combi supplies DHW and radiant boiler. Manual fill line to boiler no problems with that. Just the peky PRV that allows the pressure to creep up during next 5 to 10 minutes.
    Open a faucet and pressure goes quickly to set point, then creeps up.
  • STEVEusaPASTEVEusaPA Posts: 3,691Member
    Do you have a back flow preventer on the water service coming in?
    For the PRV, I guess your options are:
    -Take it apart, try to fix it.
    -Replace it
    -Put in one of these

  • hot_rodhot_rod Posts: 12,402Member
    Usually some dirt , teflon tape, etc stuck in the seat. Disassemble and clean will usually fix the creep.

    Wait too long and you may get a groove worn into the brass seat, then a replacement is required. Which should of course be the easily serviced Caleffi pictured above. :)

    Simply unscrew the grey plastic hex to expose the screen and working parts.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • nibsnibs Posts: 383Member
    Saved by the wall.
    54lbs and holding.
    Thanks @hot_rod for telling me to take it apart, enough sand and gravel to start a business. Had a new strainer on the shelf, so put that in to try to get the crud before it hits the PRV.
    The brand of PRV installed is a bear to clean, very skinny O rings that need a bit of grease to keep in place for re-assembly, the O ring at the back stayed in the housing and fell into the supply pipe, the screen hangs up and is quite hard to get out without damage. Got pretty good at re-assembly by doing it about 5 times.
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