Blackwater Valve

[dale farley]

Jim, The one thing I don't understand is that if it is really a clog, why would it drain fine as soon as I push the valve back in to about 1/4 open. That would seem to be reverse logic. You would think if it is clogged when open all the way, it would surely be clogged when only open 1/4 the way.

There surely must be a logical explanation to this if it is happening to others. It has never been a problem, just a mystery. I am considering the disassmbly of my valve just to see how it works. I am surprised that someone hasn't taken one apart and has a picture of it.

[Jon Wehrenberg]

Whatever you do, do not, I repeat, do not get down there and look up that pipe to see why it drains slow.

[JIM CHALOUPKA]

I read somewhere recently that according to consumer report that Charmin, and Angel Soft toilet paper disintegrate quickly.
It might be worth a try of either of these, before you bothered to disassemble anything.

It is possible that if paper is blocking the knife (guillotine) valve that when one pushes the valve even partially closed that, that movement is enough to cut and dislodge the blockage.

You could drain and thoroughly flush your tank, then to make a test refill the tank,(with clean water only) and drain it as though it were black water. If it acts the same as with real black water you can then check for a venting problem.
If the water drains uninterrupted and in a fashion acceptable to you, then look at the tissue issue, or perhaps something more substantial as the culprit.

I don't think it is the valve itself per se. If the valve moves freely and seals whatever it is controlling then it should be OK. If there were a material lodged in the valve permanently, then it would (never) function properly.

[gmcbuffalo]

I'm with Jim on this. Vent problem. With the valve wide open the fluid is going out faster than air can replace the space, and it can not gulp air thru the hose so the flow stops.

Does your washer/dry vent into the black water vent pipe, possible causing lint to build up in the vent pipe.

GregM

[Petervs]

I once did an experiment to see how toilet paper dissolved. Put a sheet in a bowl of water for a few days. Tried several different brands. Most do not dissolve at all.

The RV specific brands do fall apart after about 3 days.

[dale farley]

Since we use the same toilet paper that we used in the Marathon, I am inclined to believe that the paper is not the culprit. I never had a problem with the Marathon. I am wondering if it is something with the design of the system that causes a vent or draining problem.

[Jon Wehrenberg]

If this was a venting problem I am certain Dale would hear the oil canning as the tank drains, then bubbles work back up through the drain to restore atmospheric pressure to the inside of the tank. Also, before that happened he would hear every trap inside the house, in the shower, the sinks, etc. being sucked dry. Paulette would hear each trap gurgling as air is pulled through them.

It isn't a venting issue.

[JIM CHALOUPKA]

In the opening post, Dale stated that if he reduces the flow to 1/4, then the tank drains just fine.

That says to me that the valve will flow freely, because there is a venting to the tank that will support that flow.

If the tank valve is open full then possibly there is not enough venting to support full flow?

The valve at full flow could , because of the configuration of the fittings, and or the area where the valve is mounted, be causing a turbulence that disrupts the flow?

What is not known is if that particular tank and valve combination ever drained the way Dale expects it to, nor if the valve in question is the original valve, or some replacement by a past owner, or if there is some article submerged in the tank that is moved over to the inlet to interrupt the flow when the valve is at full flow, but held at bay at 1/4 setting to allow draining?

The tank could be oil canning and Dale has not heard it. I think his tanks are polyethylene, and not stainless, and would have a much quieter and dull sound to them. They could also be covered in insulation?

I am only guessing here as is everyone else. It's now up to Dale to take it apart and come to a conclusion.

[truk4u]

Dale,

Did you not read what I posted? Take the valve apart.

[rfoster]

Has Jdub been in your coach?