Sewer flush

[scrowba]

Hello all,when I hook up my hose to the sewer flush on my unit the water comes out from my water vent underneath my sink in the bathroom. I have all my lines open to flush. Any ideas of why this is happening? Thanks

[jimcol]

Not sure on your model but on many of the models the check valve for the black tank flush is under the lavratory sink. They do go bad and have to be replaced. Not a big deal to replace and are available at most RV type stores. Let us know what you find. Jim

[Trailer Trash 2]

I agree with jimcol the vacume braker is stuck or no good it is a warintee job or a out of pocket. I dicconected mine being the inlet hose is 2 feet higer than the tank and for it to travel up that hose would be a task, and besides when have you ever heard that Poo travels up hill ? never it always goes down hill, I got a duble male El and screwed the two loose ends together I now have very good pressure to the spray nozel in the tank.

[sreigle]

Agree it's likely the antisiphon valve. Look under the lavatory and you'll see two vertical lines. The crossover between them is the valve. It's something like $32 for the valve from a dealer so that's why many just loop those two lines together without the valve.

[carlson]

Steve,
On our 3400 RL, the valve is in the upper cabinet that is in the Kitchen that backs up to the shower.
The hose actually runs in the pock door opening.
If you open the cabinet and see one of those hide a plate with 4 corner screws in it, take the plate off and that is where the valve is.
Well that is were mine is.
Karl, is yours a front living room, so the bathroom is towards the back.
I think the anti siphon valve has to be up high, so if you have one of those blank hide a plate up high check it out.
The other guys maybe right, but mine is up high behind the plate.
Sorry this probably doesn't help, hope it is not a loose fitting.
E. Sven

[2 for Him]

Must be the anti-siphon valve, I can't see how water going in the black tank could cause a leak in the grey water system. If you remove it, put an anti-siphon hose bib valve on the inlet connection, or "poo" will travel uphill and back down into your hose ect. when disconnecting.

[sreigle]

Carlson, that's where it is on our 3400, too, except ours is behind the wall in the middle level of the pantry. On our 3295RK it was under the vanity. Since he mentioned water leaking in the vanity I assumed his is there. But I've been wrong many times before!

[carlson]

Steve,
I guess my question is.
Wouldn't the anti-siphon valve have to be mounted at a height higher then the outside connection?
To my knowledge, it would brake the siphon between the outside flush hose connection and the black tank, and wouldn't it have to act like a check valve so sewer gases would not come out of the black tank to inside the coach.
Just a question, I do not know the layout for the 3685FL, , but it is a front living room unit so the toilet, sink and shower would be in the back.
Just wonder.
Thanks
E. Sven

[sreigle]

I'm not an expert but your explanation matches my understanding. I think it is supposed to be the highest point between the outside connection and the tank. I'm sure we have people here with professional working knowledge of these things who can speak to it better than I can.