Flooded Interior - Anti Siphon Valve

[leeines]

I recently awoke at night and found the bedroom carpet under water. I turned off the city water supply outside. I traced the problem to the anti-syphon valve under the bathroom sink.
Drawing water from the fresh water tank with the onboard pump did not produce any leakage at the valve. Turning on the city water produced a flood out of the valve again.
I am very concerned about the OSB flooring which is unprotected, has no water barrier on it. I cut the carpet in the bedroom, dried out the OSB there, under the sink and under the shower stall. Should I tear up the linoleum in the bathroom?
I disassembled the valve, found nothing wrong internally.
At our next camping stop, I turned on the city water supply and there was no flooding from the valve. It has worked properly ever since.
What would cause the problem? What can I do other than replaceing the valve?
What should I do about the OSB under the bathroom linoleum? The OSB is now dry under the shower stall and sink and in the bedroom.
Thanks in advance for any answers, advice and so forth.
Lee 2007 Monaco Knight 40 PDQ

[AFChap]

I see no other comments ...

I read this message this morning and have thought about it off and on all day. On my MH, the ONLY WAY I can think of for water to come out the anti-siphon valve under the bathroom sink would be if I had connected to the black tank rinse inlet and turned on the water hose and overfilled the black tank ...and I know from experience (yep, I have done it), if the bathroom sink drain is not closed it will actually overflow the sink on my coach rather than come out the anti-siphon valve. (and yes, the water "looked" clean)

Is it possible at the first stop that you had the shore water hose attached to the wrong inlet in the water service bay?? ...on my MH, they look identical except for the labels, and I can imagine if I were tired and/or not paying attention ...or if someone not familiar with things hooked the water up ...the hose could get connected to the wrong inlet.

...I can think of no other way for water to come out the anti-siphon valve under the sink ...or for water to even be present in that vent pipe ...than an overfilled waste tank.

As far as drying out the floor, it sounds like you have done what you can. I doubt much would soak into the flooring under the linoleum ...when I did the deed water was actually flowing out the bottom of the MH through a wiring/plumbing access hole under the bathroom cabinet.

[Norm4015]

I agree, the anti-syphon valve under the bathroom sink is part of the black tank flushing system and it has no connection to city water or the fresh water tank. A friend connected his city water hose to the black tank flush and went inside and turned on the TV. His wife caught the problem before it did any real damage. I saw him flying out the door and running to turn off the water and he admitted his mistake.

[leeines]

Paul and Norm,
Thank you for your replies.
I know for sure that there was no water to my black tank as the hose to it was not connected, so the mystery still exists. I will have to resort to calling Monaco, which I hate to do.
Thanks again!
Safe travels,
Lee

[speed racer]

The anti syphon valve is part of the sewer system most of the time the gray tank only because the only thing hooked to the black tank is the toilet and it has it's own vent. They need these valves to prevent water from syphoning from the Ptraps in the sinks and shower and washing machine if so equiped.

[Gary RVRoamer]

Agree with the others - the anti-siphon is in the sink drain line, not the fresh water system. No way the city line would leak out there.

As for the OSB, you will have to inspect to see if it is still structurally ok. If the glue has deteriorated, the fibers or chips will easily come loose or crumble from the surface. Not much to do except replace it if that's the case, though I have had some success stiffening it back up with copious amounts of shellac. Or perhaps a dry rot reapir resin such as Git Rot.

[leeines]

Gary,
Thank you very much for your reply.
Fresh water was definitely coming our of the top of the anti syphon valve. The line that was gushing water was the one that comes into the side of the valve. The other line comes out of the bottom of the valve.
I am puzzled as to where each line originates.
Can you help me with that question.
Thanks in advance for your reply.
Lee

[OldChief7155]

Can you go to the manufacturer's website and pull up a plumbing diagram? It might show where the side line comes from.

[Gary RVRoamer]

A picture would help. Perhaps that is not an anti-siphon valve.

Are the water lines in question 1.5" PVC or ABS drain lines or 0.5-0.75" tubing for fresh water?

[Norm4015]

Quote:

Originally Posted by Gary RVRoamer A picture would help. Perhaps that is not an anti-siphon valve. Are the water lines in question 1.5" PVC or ABS drain lines or 0.5-0.75" tubing for fresh water?

I agree that a picture would help. I had to repair an anti-syphon valve in my motorhome and I replace one in a friend's motorhome. The purpose of an anti-syphon valve is to prevent black water from entering the fresh water supply. There are no anti-syphon valves on the fresh water side.

[Gary RVRoamer]

It seems evident from the symptoms that whatever that valve may be called, it is in the fresh water system and is pressure sensitive. I'm guessing the city supply pressure was high enough to cause a failure, while the onboard pump @ around 45 psi was not.