Pressure valve? leak on Cougar

[Howie]

Can someone help me on what this valve is? It is located underneath the bathroom sink that has 2 white water lines running to it. When I attached the hose outside to do a power flush of the black tank I noticed water running down the white lines from the bathroom down into the convenience center in the belly storage. The lines go straight up to the underside of the sink and the black valve sits with the black protrusion on the top of the valve. I found that this valve was leaking and I don't know if it is the attachment threads or the valve itself yet. It does not leak when I am attached to city water, only when flushing the black tank. I will investigate tomorrow when I can get back to it. I attempted to attach a picture with no success.

[sourdough]

It's the backflow preventer for the black tank flush. It may be installed backwards or defective. You can get them at a hardware store, or, I've seen RVs where the preventer is removed and just replaced with a piece of tubing - as long as you keep the water lines up high with the loop. If it were me I would just buy another valve. It could also be that something is loose or installed improperly. You will have to look at it more closely to determine that.

[JRTJH]

I believe you have a 2015 Cougar ??? If so, and if you didn't winterize or remove that valve last winter, chances are it froze and is broken. It is the black tank anti-siphon valve, designed to prevent backflow of black tank contents/gasses into the city water supply if you left the black tank flush connector attached to your hose.

I'd think, if it works when you flush your black tank, it isn't connected backwards. That leaves loose connections, usually they are only hand tightened, so you can reach under the sink and tighten them sufficiently. If that doesn't work, then it's probably freeze damage and the valve needs to be replaced. There isn't any repair that I know of. You can find an exact replacement at any RV parts store, Amazon, EBay or most of the internet RV parts sites. You can also, as Danny said, go to Lowe's/Home Depot and get a replacement in the plumbing supply or irrigation section.

I wouldn't delay the repair if you intend to use your black tank flush system. If it's cracked and leaking, it's only a matter of time before the crack becomes a split and you "flush your entire bathroom"... Even though it's clean water, that winds up being a mess to clean up.

[Howie]

Thanks you guys for the help. I called the dealer and the service desk wasn't any help as the person I spoke to had no idea what it was for. As usual the forum members know just about everything.

It was both fittings that were slightly loose causing the problem. I got them as tight as I could using my hands as the space was so limited. It did stop the leaks so all is good. My guess is that the previous owner never flushed the black water tank using hose connection as there isn't any water damage under the sink I could see.

[Pmedic4]

Ours failed, water gushing out from under the vanity, so bought the RV replacement mostly because it was a simple R&R. There are brass versions which are actually less expensive but you'll have to buy additional fittings to hook it up so the cost difference is net zero, plus making sure you get what it requires. Since I'm the kind that makes 5 trips to the hardware store for the typical plumbing problem, the standard part was my choice😀.

[bobbecky]

You are very fortunate that this back flow/air gap valve is located where it is. On our rig, it is between the back of the shower and the back of the pantry cabinet, but we are full time, so it has never experienced a freeze and is still working with no leaks, and we usually drain the black tank and flush it on a weekly basis. The photo shows our valve, peeking past the sliding door.

[russmathias]

Thanks everyone. We’re new full timers and I have just noticed water, I believe may be black water, in the belly, under the storage area. Do you think this valve could be the issue. Howie, I hope you get yours fixed. Any thoughts will be helpful. Thanks again.

[Howie]

russmathias, it could be from this valve but one way to verify or eliminate would be to hook up the back flush to your hose and turn it on. You could then verify visually if this valve is the problem because you will be able to see the leak and the water will run down both of the lines attached and the water will flow down and end up in the underbelly. If there is no leak from this test then you know the water is coming from somewhere else and you need to drop the underbelly to inspect.

[russmathias]

Great advice. Thanks Howie