Forum Discussion

Mikesr's avatar
Mikesr
Explorer
Oct 02, 2017

Black Tank Flush Vacuum Breaker

Had a major water leak today while operating the black tank flush on our 2017 Outback 325BH. After turning the water off and cleaning up the majority of the mess I went in search of the source. Turns out it was the vacuum breaker under the bathroom sink. Checked the fitting for tightness and had D/W turn the water back on, still leaked. I decided to remove the vacuum breaker to get a better look at it. Seemed fine but I was suspicious of something clogging the breaker. Forget to mention when the leak was discovered we had a super strong odor of stink bugs in the bathroom. Well after shaking the vacuum breaker and flushing water through it in the kitchen sink low and behold a drowned stink bug emerged. Ok so tonight I’m doing my research and found this is common. The vacuum break still has a slight leak so tomorrow I’m calling the dealer and asking for a replacement. My biggest question is how did this stink bug get into the vacuum breaker? Could have it damaged the seat or internal seal of the breaker ? Should I replace with a brass vacuum breaker ?
Thanks for any suggestions.
  • BB_TX's avatar
    BB_TX
    Nomad
    Oct 02, 2017
    Does your hose connection have a screen washer on it? If not it could have crawled in there. Also, if like mine, it could have gotten in under the top cap of the valve.

    Those valves are notorious for leaking. One of the pipe fitting nipples broke off mine and flooded the floor before I could get it shut off. I replaced mine with a piece of pipe and use an external anti siphon valve.
  • Mikesr's avatar
    Mikesr
    Explorer
    Oct 02, 2017
    BB_TX wrote:
    Does your hose connection have a screen washer on it? If not it could have crawled in there. Also, if like mine, it could have gotten in under the top cap of the valve.

    Those valves are notorious for leaking. One of the pipe fitting nipples broke off mine and flooded the floor before I could get it shut off. I replaced mine with a piece of pipe and use an external anti siphon valve.

    Yes I checked the inlet and it does have a screen.
    Thanks for the input
  • dfletch's avatar
    dfletch
    Explorer
    Oct 02, 2017
    I am still amazed they run it up into the bathroom vanity when there is room behind the panel where the inlet is to provide enough rise to prevent siphoning.
  • BB_TX's avatar
    BB_TX
    Nomad
    Oct 02, 2017
    dfletch wrote:
    I am still amazed they run it up into the bathroom vanity when there is room behind the panel where the inlet is to provide enough rise to prevent siphoning.

    Mine was in the wall between the shower and my entry closet, in the pocket door wall. I had to cut a hole in the back of the entry closet and, with the pocket door pulled out of the pocket, could reach in and remove the valve. About 4' above floor level.
  • Old-Biscuit's avatar
    Old-Biscuit
    Explorer III
    Oct 02, 2017
    Black tank flush 'anti-siphon vacuum breaker backflow preventer' is OPEN to atmosphere around top cap.

    Flush water comes in bottom, pushes a disc up which seals OPEN area and water then flows out thru side to the nozzle in tank.

    When water supply is turned off, disc falls back down closing off bottom thus preventing backflow. When disc drops it also breaks any vacuum in line by exposing opening to atmosphere ---tank side

    Too high of water pressure and it can leak out top
    Disc not fully sealing off top area and it will leak out top




  • Mikesr's avatar
    Mikesr
    Explorer
    Oct 02, 2017
    Old-Biscuit wrote:
    Black tank flush 'anti-siphon vacuum breaker backflow preventer' is OPEN to atmosphere around top cap.

    Flush water comes in bottom, pushes a disc up which seals OPEN area and water then flows out thru side to the nozzle in tank.


    Great information thank you.
    That would explain how the stink bug got into the vacuum breaker.
    I’m wondering if placing a soft screen meshing around the valve will help or possibly cause a different problem ? I’m thinking zip tie the material loosely around the vacuum breaker?
    Any idea what would attract a stink bug to th vacuum breaker ?
    Thanks again
  • neschultz's avatar
    neschultz
    Explorer
    Oct 02, 2017
    When mine went bad the Specs also said it needs at least 20 psi to seal when the water is turned on so make sure you turn the water all the way on or it just runs out the top.

    I replaced it with this Brass check valve from Lowes. And a 1/2” ell.
  • Lynnmor's avatar
    Lynnmor
    Explorer
    Oct 02, 2017
    My breaker is on a shelf in the barn causing no problems. These things are to be installed in a place where expelled water will cause no problems but manufacturers can't read the instructions. With a check valve in the inlet, they serve no purpose.
  • sbell2003's avatar
    sbell2003
    Explorer
    Oct 02, 2017
    That is too funny! I had a stink bug get in mine this summer. Took the valve out and blew on it only to see a stink bug fly out. Put it back together and it has been fine since.
  • ktmrfs's avatar
    ktmrfs
    Explorer II
    Oct 03, 2017
    well, the typical vaccuum breaker in a TT/5v'r that's made of plastic is prone to failure. Not a high failure rate, but enough failures like you mention. My RV dealer parts guy says they have customers come in with failures like you mention, which I had also. Best solution is to replace it with a quality brass vacuum breaker. a few bucks more but much less failure prone.

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