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Old 10-29-2017, 12:20 PM   #1
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Join Date: Aug 2016
Posts: 568
RP-171, relocation of black water flush system atmospheric vacuum breaker/check valve

Last year I had the flush system atmospheric vacuum breaker/check valve blow water between the bedroom and bathroom walls when trying to flush the black water tank.

The proximal cause seems to have been a stink bug that managed to crawl into the vacuum breaker, preventing it from closing off properly when pressurized.

I vacuumed the water off the floor, cut a hole in the bedroom wall to access the valve (!), cleaned it out and tested it, then put everything back together.

The particular flushing system I have is a B&B Molders Flusher 2. I found the installation documentation online and read it carefully. I noted a few things:
  • "Vac/Check should be located a minimum of 6" above flood rim of highest fixture connected to waste holding tank." Note: In my trailer, installation is only 4" above toilet rim.
  • "Minimum water pressure of 40 psi must be used."
  • "Make sure faucet is open completely during entire tank flush cycle. Vac/Check is designed to work at water pressure range of 8–125 psi." Note that this implies that one shouldn't ease the water on, but turn it on rapidly.
  • "Water leakage from Vac/Check is likely when water pressure in supply line is under 8 psi."
  • "It is normal for a small amount of water to escape Vac/Check as plumbing line for tank flush pressurizes." So mounting the valve in an inaccessible place inside a wall is not an example of competent trailer design.
With this as a starting point, I'm planning to relocate the vac/check valve from its position in the wall to under the valance of the bathroom sink so if/when it leaks the water can go down the shower drain rather than onto the floor. I have done a bunch of inspection and measurement, and it ought to be a simple and manageable modification. Based on floor layouts, it looks as though this would work in all R-Pod models except perhaps the RP-182.

When I actually make the modification, I hope to post photos and results on this forum.

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Old 12-11-2017, 10:52 AM   #2
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Join Date: Aug 2016
Posts: 568
The deed is done, with valve on right hand side of bathroom sink valence.

Required about 15' of 1/2" PVC braided tubing, note that it needs to be 11/16" OD so as to accept PEX clamps. Pulling the tubing through under the bathroom floor plan was a PITA.

I used brass fittings except where fresh water comes in without room to tighten a Sharkbite swivel ell, so I used plastic. My apologies about picture rotation.
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johnbryanpeters is offline   Reply With Quote

black, black water, breaker, cat, check, flush, location, valve, water

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