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Leaking Backflow Preventer

Hi, I've got a Conbraco backflow preventer on the water feed to my boiler. It drips out the bottom maybe every 3 seconds. I don't have any idea where to start in fixing this drip, and i want to make sure that it isn't indicative of failure...perhaps leading to drinking water contamination.

Anyone have any tips on fixing these?

I think the model number is 40-203-02.




  • crash2009
    crash2009 Member Posts: 1,484
    Mine drips a bit too

      Not sure if this is normal.
  • Jamie Hall
    Jamie Hall Member Posts: 23,433
    Not sure

    but I think that model is a reduced pressure zone valve with a relief vent.  If the relief vent is dripping -- which sounds like what you are describing -- it means that one of the two check valve assemblies is leaking.

    And should be replaced; I'm not sure it's repairable.  Sorry about that.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Abracadabra
    Abracadabra Member Posts: 1,948
    repair kit

    Conbraco Model #40-203-02 has a repair kit no. 40-003-94 
  • tim smith
    tim smith Member Posts: 2,765
    Re: leaky backflows

    A lot of the time it just needs flushing out. Pull checks out below square headed caps and clean off bottom of plastic plunger where rubber gasket is. Flush out receiver ports and put check (s) back in. Most of the time it is debris under the check seats.  Needs to be done by someone who understands how to shut off water flow to it and backflow construction or you will have problems. Also if you do not put back in correctly they will be problems.
  • a2shutt
    a2shutt Member Posts: 97

    I'll look into flushing it out and if that doesn't work, I'll get the repair kit.

    Shutting off the water seems straightforward, as there is a ball valve on either side of the valve body. I'll do some research and find out how those work. I'm as smart as any plumber :)
  • RJ_4
    RJ_4 Member Posts: 484

    Installing a brass wye stainer ahead of backflow will keep backflow  clean.  Also on a job I had a backflow dumping water, found ruptured checks inside backflow (Febco 825y ) .  Backflow was servicing a steam boiler in a 5 floor nursing home.  Boiler was on roof and building had a terrible water hammer problem in the domestic water piping ( thats another issue ) I found that water hammering and a unusual press drop at inlet to backflow was causing damage to internal checkvalves.  I installed a brass spring check valve ahead of the backflow, this took care of the problem untill the the water hammer issue is resolved.

    There was an error rendering this rich post.

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