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2nd Backflow Preventer Leak - is this common?

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jlonj
jlonj Member Posts: 23
I'm trying to figure out if I just have bad luck with these things, or if it's a symptom of another problem.

I had an issue last year where my steam boiler started slowly gaining water. I have a manual fill. The backflow preventer then started leaking a few weeks later. My theory was the the manual fill ball valve was leaking and causing everything, but my new plumber (old one went out of business) was skeptical. The plumber replaced the preventer, but when the boiler still kept gaining water, he also replaced the manual fill a few weeks later. Since then, the boiler stopped gaining water, but this was towards the end of the heating season early this year.

Now, I'm having my boiler serviced, and the new backflow preventer started leaking right after the servicing. In the process of replacing it too.

I'm trying to figure out if these are just 1) crappy backflow preventers, if i have 2) crappy manual fill ball valves (i guess we'll see after this preventer is replaced), or 3) there is some other issue - does my boiler have something wrong that's causing pressure differentials in the water line.

Comments

  • hot_rod
    hot_rod Member Posts: 22,157
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    Usually if multiple BFDs leak there is something causing it
    one common cause is pressure spikes caused by fast closing valves. Solenoid valves for example.
    if you have high water pressure it makes it worse. A couple suggestions, add a water hammer arrestor 
     Or sometimes a swing check upstream of the VFD to take the hit from a pressure spike.
    unless it is corroded or a ripped seal, the drip indicates it is doing its job😉
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • ChrisJ
    ChrisJ Member Posts: 15,702
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    Are you on well water?
    Any filters, or strainers?

    Ever find debris / specs in your aerators on faucets?
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    edited October 2020
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    If you manually feed, why not put and close ball valves upstream of BFP and a second one between the BFP & the water feed.

    There was an error rendering this rich post.

  • ethicalpaul
    ethicalpaul Member Posts: 5,704
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    If you manually feed, why not put and close ball valves upstream of BFP and a second one between the BFP & the water feed.

    I did just that. I'm glad it wasn't a crazy idea. That vent port on the BFP made me nervous!
    NJ Steam Homeowner. See my sight glass boiler videos: https://bit.ly/3sZW1el
  • ChrisJ
    ChrisJ Member Posts: 15,702
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    If you manually feed, why not put and close ball valves upstream of BFP and a second one between the BFP & the water feed.

    I did just that. I'm glad it wasn't a crazy idea. That vent port on the BFP made me nervous!
    Mine is wide open over my head in the basement.
    :D
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
    ethicalpaul
  • JUGHNE
    JUGHNE Member Posts: 11,062
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    I wonder if a full flow of water thru them would clean the sediment out from under the seat.
    If they are passing water from just a leaky valve then not much flushing action going on there.
    A full port bypass would pass a lot of water. You could even put a boiler drain below the BFP.
  • hot_rod
    hot_rod Member Posts: 22,157
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    Depending on what model you have they usually have a screen on the input side. Some installers trash the screen as it slows flow when it plugs. Excessive teflon tape is one culprit.

    By code, that vent port should be piped to an indirect drain, floor drain, or within a few inches of the floor.

    In this type of BFD, three main seals that cause leaking, both concial checks, and on the center cylinder that closes off the drain port as soon as pressure is applied. They disassemble easily and can often be cleaned and put back into service.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • ChrisJ
    ChrisJ Member Posts: 15,702
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    hot_rod said:
    Depending on what model you have they usually have a screen on the input side. Some installers trash the screen as it slows flow when it plugs. Excessive teflon tape is one culprit. By code, that vent port should be piped to an indirect drain, floor drain, or within a few inches of the floor. In this type of BFD, three main seals that cause leaking, both concial checks, and on the center cylinder that closes off the drain port as soon as pressure is applied. They disassemble easily and can often be cleaned and put back into service.
    Depends on the area.

    I specifically asked the inspector and he okd mine as well as in person.

    Should I plumb it somewhere?  Probably, but I haven't in 10 years.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • clammy
    clammy Member Posts: 3,111
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    I have always installed a ball valve after bfp and had the home owner use that to fill boiler . I have found that they last longer having pressure on then those that see no pressure till feeding water that s when they usually leak . I also do see what the house water pressure is and it extremely high I ll add a prv no sense in exposing a auto feed to excess water pressure . Some towns have hi water pressure where I live it’s not uncommon to have over 150 to 180 psi durning the nite . Peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating