Water leak under bath vanity

[Butch & Kathy]

Packing up after a great trip to St Augustine and noticed a leak in the basement under the bathroom in our 3160RL. In addition to the hot &a cold pipes there are two white water lines under the sink connected together with a black contraption (backflow prevention?). The black contraption is leaking suddenly. Any suggestions?

[kdeiss]

You just may need to tighten the connection to the black flow valve worked for me!

[Butch & Kathy]

More info. Neighbors tell me it's an air admittance valve. Grey tanks show 2/3 full. Maybe they are really full.

[Butch & Kathy]

Now I learned that it is my black tank flush back flow valve. Any one else had this problem?

[Irlpguy]

quote:Originally posted by Butchy

More info. Neighbors tell me it's an air admittance valve. Grey tanks show 2/3 full. Maybe they are really full.

The "black" thing you refer to is indeed the back flow preventer, some are located in the same place as yours and mine and some are in places that are not as easy to access.
I first replaced mine when it leaked only to have it leak again so I removed it and connected those two pipes with other fittings. I have had no concerns or problems with it since. I use a fitting with a valve built in when I connect to my black tank flush line, I shut it off while it is flowing before removing the hose, I then open it up which drains the line from the replaced fittings back to the valve.
The back flow preventer is intended to prevent water from flowing back from the black tank, in order for this to syphon back the black tank would have to be full above the entry point into the tank, since you have just flushed and drained your tank this is not possible.
My opinion is this may be a requirement but is a joke and is not needed.

My advise is to replace it with fittings and go on your merry way. By the way this has no bearing on your Gray tanks and I would not trust the lights to tell me how much is in "any" tank.

[DQDick]

As Iripguy says, it's the backflow preventer. I just took it out, connected the two lines and use a backflow preventor intended for outdoor faucets on the end of the water hose I use for black tank flushing. Safer and no failures in 6 years of full timing.

[BB_TX]

Yep, you are just the latest of many of us who have had that anti-siphon/backflow prevention valve fail. Some have replaced in kind. And as noted, some of us eliminated it and use an external valve.

[mlh]

Yes I have a suggestion, take it out and throw it away. I will bet that it will never leak again.
Lynwood

[Butch & Kathy]

Thanks all. It will be gone tomorrow.