Black Tank Flush Vacuum Breaker

[Mikesr]

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.

[ktmrfs]

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.

[sbell2003]

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.

[Lynnmor]

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.

[neschultz]

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.

[Mikesr]

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

[Old-Biscuit]

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

[BB_TX]

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.

[dfletch]

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.

[Mikesr]

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

[BB_TX]

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.