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Backflow Preventer vent drip

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?



  • Jamie Hall
    Jamie Hall Member Posts: 22,089
    Something got stuck...

    under the seat of the second check.  Or the second check seat is damaged.  That happens -- and that's one reason for the vent, to show you that one of the two checks isn't working.

    For a 9D, so far as I know the best option is to replace it.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • billtwocase
    billtwocase Member Posts: 2,385
    Replace it

    preferably with something other than Watts, Conbraco perhaps. I always tell my customers that turn off their main to just shut it off, and walk away. Most people will flush a toilet, or run a faucet until it stops. Pressure is what seats these valves, and when that is gone, the vent opens and leaks. Sometimes they stop, sometimes they don't.
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