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hh409 Member Posts: 14
hello all

PARTICULARS - boiler works to heat the house and supply hot water, system is about 15 years old with no significant problems to date.

the cold water supply line feeds into a WATTS 1/2" 9d-m3 backflow preventer with intermediate atmos vent, that then feeds into a WATTS #S1156F pressure regulator.

PROBLEM - i noticed that when i turn the house water supply off a small amount of water drips from the vent on the backflow preventer, this usually stops within a few minutes. last night i turned the water on without incident but now the backflow preventer keeps dripping water and will not stop.

this is a vacation home so lately we have adopted the practice of shutting the water supply off when the house is vacant. any ideas on what suddenly caused the backflow preventer vent to drip non stop?



  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    any ideas on what suddenly caused the backflow preventer vent to drip non stop?

    Dirt in the backflow preventer valve seat(s)?
  • Zman
    Zman Member Posts: 6,777
    Check valve

    The backflow preventer  is designed to vent when domestic pressure drops below system pressure.

    If you install a spring check upstream of the backflow valve, the problem will be solved.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • bob young
    bob young Member Posts: 2,177

    T he check valve is key to protect the back flow. boiler code in nyc & state insists on it or you fail inspection. a good law.  bob young nyc lic. plbr
  • Talldutch
    Talldutch Member Posts: 4

    It sounds like the device is doing it's job  when the pressure drops due to you turning off the water the first check valve is allowing water to drip out the vent and causing the second check to close   therefore protecting the supply from any unsafe water getting back into the supply side   Most of the Watts 9d vents have a tapping that allows for piping to a floor drain     Do not install any type of valve on the discharge of the vent   when  you re-energize the system the vent will close and you should have no problems   A soft seat check valve in front of the device will help with spitting problems due to minute pressure fluctuations  Hope this helps
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