Black tank flush

[Martingolf1231]

When I try to use my black tank flush system, water comes rushing out from a valve under the bathroom sink cabinet. Has anyone experienced this?

[NC Roamer]

Nope. Inflow from my black tank flush goes straight into the black tank.

[Imnaha.Mansion]

Seems to me. Maybe your black tank vent is under the sink and you are over filling the tank or your sink was hooked to the black tank and you over filled the tank or most likely the put the black tank Washer on the grey tank. Maybe test by what cones out when which valve is open and if only sink is turned on.

[Mike WA]

Originally Posted by Martingolf1231

When I try to use my black tank flush system, water comes rushing out from a valve under the bathroom sink cabinet. Has anyone experienced this?

If I'm not mistaken that's the check valve under the sink. It might be defective you'll have to get up in there and get a view of that valve. Have someone turn on the water as you watch for why its leaking and go from there...

[Martingolf1231]

When I look under the sink it looks like there is a black check valve and water comes pouring out of it when I connect to the black tank flush connection. Do you think I need to do something to that valve or the valve might be bad? Thoughts?

[Skaling]

Yup. Backflow check valve was loose. I check it every time I use it now.

[fidalgo66]

The first time I flushed mine, the same thing happened. Took it in under warranty, and dealer replaced the valve. 2+ years later, have not had any more problems.

[tnchuck100]

I'm sorry but this thread is making no sense at all.

1. The vent valve under the sink does not vent the black water tank.
2. The vent under the sink (air admittance valve) is for the grey water tank.
3. The black water tank is vented through the roof.
4. IF you have water coming from the vent under the sink AND IF you are sending water in the black water tank flush port then something has been installed wrong!

I suspect there is some misunderstanding as to what is actually taking place here. If everything is properly connected this situation cannot happen.

The question now becomes: Who installed the back water tank flusher? The owner? The dealer? Jayco?

[BigJohnD]

Some will disagree, but I've always gotten rid of the back flow valve due to the same issue. Sometimes your lucky to have it under the sink and will catch the leak. Other times, it's in a wall and damage can be done. Why take the risk. It is there to prevent anything from coming back from the tank to the inlet. The manf says it has to be installed above toilet level, so that's why you see them where you do. However, to throw a curve ball at you, if you have ever installed a Quickie Flush, No Fuss Flush, or one of the other off the shelf types, you won't see that valve in the system or in any instructions. They usually just put a vacuum break at the inlet.

So, we delete them completely by making the connection of the pex where the valve is / was, install a vacuum break at the inlet, and use a designated hose for this operation. We've gotten rid of every one of them in our 8 units, as they ALL have leaked. Guess where the one on our rig in the sig is / was? In the wall behind the shower. But, it can be accessed under the bottom bunk where it's open to the back of the shower. Think that'd cause some damage if gone unnoticed or not checked?

Food for thought.

[arkhillbilly]

It is the back flow check valve for the black tank flush. I posted about this problem in early spring. The valve mfg states "these valves will, as a normal operation, flood water at times." They are used to keep black tank objects from flowing back into the fresh water system you are hooked onto. When I contacted the mfg, they sent me a new valve post haste. Mfg and Jayco both told me they served no other purpose than back flow and as a owner, I could remove it. Removed same and used a 2" nipple. Problem solved. My 2012 Eagle 298rls had it hid behind screwed shut wood doors, about 18" above the furnace. Needless to say, that day had hours of drying out.

[namusmc65]

I know one thing for sure, before I use the black tank flusher in my unit, I will find out where that valve is located first. Don't use our black tank much for the dirty deed. Just go to the campground facilities to eliminate a lot of problems I read about on here!

[BigJohnD]

When you do find it, just delete it and your worries are over. We had a similar incident as arkhillbilly in the first RV. That one was in a wall behind the TV. We've ditched them ever since. On most, where the pex goes up to the valve, then back down again, we just rid of those pieces and make a straight shot.

[arkhillbilly]

I bought a back flow valve at home depot for about three bucks, and leave it attached to the separate hose I use for that type thing. One inch of water in my furnace was enough. I blew it dry with a hair dryer, and it worked the next day. I dreamed of dollars out the window that nite for sure.

[gijoecam]

Why anyone would put a backflow preventer inside the camper is beyond me... it should either be outside the camper wall, or emclosed and able to drain outside. Any other arrangement is just a ticking time bomb...

[arkhillbilly]

Not sure what companies are thinking. You can go to a number of forums with other brands, and the problem with that 571 valve goes back a few year. I read the set up instructions from the mfg. to a Jayco service rep, and got a big yawn! I hear most of the newer units have it by the toilet. That way when it fails to work, it can flood the bath floor and get into the underbelly!! Its a CYA , for somewhere in the owners book I read that one was not to flood the floor with water.

[WDW]

Is this an issue in Grethawks or just TTs?

Anyone have experience in GH flooding or removing it?

[arkhillbilly]

Its a industry problem. It is usually a b and b ind number 571 anti back flow valve, usually located on the black tank flush system. Can be located anyplace between inlet and black tank. Required to be above the toilet level. When the thin rubber flaps stick closed, water will flood out the top full force. It will flood the entire unit if not caught in a hurry. Mine did.

[ScratchAce]

Anyone have pics of the valve and where its located for a Greyhawk?

[Jacobsnc]

Had a flood In our brand new Precept 31UL first time we used it. Tried it a second time and did the same thing. Big flood, not good. The flood and a ton of other issues with the unit forced us to trade after one trip.

[BigJohnD]

Not sure of the brands we have had, but crap, our problem started prior to 2007. All those valves suck pretty much. I do what arkhillbilly does / did. External valve from HD or Lowes.