drips from ??? under bathroom sink

[rigmaroll]

Recently noticed a small amount of water in the cabinet under the bathroom sink. Drips are coming from a 'fitting' that connects 2 black hoses - can see one drip forming in the photo. Does not appear to be an issue with the hoses themselves or the clamps but coming from the mystery (to me) gizmo. Can someone enlighten me as to what it is & what the fix might be?

[TedS]

That is the vacuum breaker valve in the black tank flush line. Have you used the black tank flusher?

[rigmaroll]

Yes, after every black tank dump = typically about twice a week (& even more so in last few days, as part of trying to resolve an issue with black tank valve not closing fully)

[TedS]

The valve vents to atmosphere and may drip. The installation instructions advise the valve be installed when drips do no harm. I don't know why installation is inside a cabinet or wall. The-Flusher2-Install-.pdf

[Country Campers]

This valve will release a small "spurt" of water when activated. On our previous TT we noticed our pans had a few water droplets on them once and a while and it took me forever to find this valve. When using the black tank flush the first rush of water going thru the valve omitted a spurt of water before the valve closed. This is normal operation of the valve, but the spurt will increase over time as the valve wears out so it is important to keep an eye on the valve, easy in your location many have there hidden behind a wall or shower controls. I am not very fond of this valve and its usage in the RV but it is what it is.

Brian

[rigmaroll]

Thanks both for the info. When the time is right should I replace with the same/OEM valve or is there a better alternative?

[Cate&Rob]

Thanks both for the info. When the time is right should I replace with the same/OEM valve or is there a better alternative?

There is no “better alternative”. All vacuum break valve manufacturers advise that their valves will leak a small amount of water when initially pressurized or depressurized and working correctly. These valves are a requirement of RVIA (Recreational Vehicle Industry Association) . . . for good reasons. The best that you can do is plan for these small leaks and capture the water so that it does not do damage. As referenced earlier . . . this is more difficult for those of us with this valve hidden inside a wall. At least yo can see and monitor yours.

Rob

[TedS]

Valterra has one, but not cheap. There are brass ones like Watts, too. Somewhere I saw one advertised as drip-less. Search AVB, atmospheric vacuum break.

[pvduke]

Same thing in my Reflection. If I flip on the water from the park service hook up too fast it goes ripping into the water board, up the hose to the VB under the sink, purges here and there then whooshes into the BT, and, not it's uncommon to find a few or a lot of drips in the cabinet so I toss a towel down first, and, now I crack it open slowly, and the VB sings a little, wait a minute for air to purge then I slowly open the park tap all the way to flush the BT. I'm full time, keep my black valve closed and I dump/flush every 3 days or when 2/3 full indicated (and here's a tip- don't toss paper in your toilet, it gets stuck on the walls of your black tank and does a number on everything including holding onto odors. I toss my paper waste in a receptacle next to the toilet and keep it out of my BT. Sounds weird but it works).

Funny story: today I was doing the flush as usual but playing with running water after two cups of joe and well....nature called. Used the head and stepped on the "gas pedal" after my quick 10-100 then went back outside to monitor the flushing and as soon as I rounded the corner WABAM! from inside the coach like a bowling ball landed on the floor- and I don't bowl! Stop the flush, unhook, look underneath and no guts are hanging down, remove and look behind the black walls, look for a blown up tank and bits, flying hoses- nothing. Man that was loud. Quick run inside and look fort the dog he's up in my chair looking at me going WTH man!, run around then into the head and something must have gotten way out of whack while flushing the BT and stepping on the gas pedal vacuum-wise cuz the VB vomited all over the place. Clean up the water Do another check and carry on with the flushing of the BT good to go. Scared the beans outa me! First time I used the head during a BT flush, and I read the OM a couple of times, but maybe I missed something about not doing that- and I'll never do that again, good thing I was NOT sitting down in there when it happened! hahahaha.

-pv.

[familytruckster4]

When the valve fails (not if it fails) I typically replace it with an elbow to permanently solve the issue. I have a brass vacuum breaker (available at most Home centers for less than the replacement in the trailer) on my flusher hose that serves the same purpose. Most RV parks also have vac breakers on the water outlets .
Since the flusher line typically has a rise in it I have never had an issue with water not draining from it for winterization.

[TedS]

Here's an idea for the location of the vacuum break valve. May or may not be pretty installed to drip into the sink. The screen shot is of a salon sink vacuum break valve.

[Cate&Rob]

I crack it open slowly, and the VB sings a little, wait a minute for air to purge then I slowly open the park tap all the way to flush the BT.

Note in the info linked by TedS in post #4, the vacuum break requires at least 8 psi to close the valve. Thus, slowly pressurizing the flush system may lead to a greater water leak. Some who leave a hose connected to the black tank flush (never a good idea for a lot of different reasons) have experienced a greater vacuum break "leak" caused by solar heating of the outside hose creating a very low pressure water volume increase that comes out the vacuum break valve since this is not enough pressure to close the valve.

Rob

[Lonestar]

OK, I need some education here. I thought I was pretty knowledgeable on RV plumbing but I didn't even know I had a vacuum break valve until recently.

What is the purpose of a vacuum break? Is there only one in my trailer, and is it just in the black tank flush line? I have a 2020 273MK, so where should I start to look for the vacuum break's location?

thanks in advance!

[TedS]

The purpose of the vacuum break valve is to prevent siphoning black tank fluid back in to the fresh water source, the potable hydrant water. It may be under the bathroom sink. It may be in a wall, e.g. the shower wall. It's elevation must be above the rim of the toilet.

[Lonestar]

The purpose of the vacuum break valve is to prevent siphoning black tank fluid back in to the fresh water source, the potable hydrant water. It may be under the bathroom sink. It may be in a wall, e.g. the shower wall. It's elevation must be above the rim of the toilet.

OK, got it.

Sounds like a good safety feature, but brings up the question, since the black tank has a vent, unless the flush outlet in the tank were below the black tank liquid contents, how would siphoning occur? I can't imagine that anyone would flush the tank before draining completely it.

I have used my flush a couple of times, but since I have a place to drain my tanks at home, I usually fill up my black tank by running water through the toilet, then dump to clean tank. I wonder if this gets the tank as clean as the flush?