Black water Full valve stuck closed

Here is the latest in our saga of the black water tank:

Several responses hit it right on. Guess my ignorance of the systems on a travel trailer are worse than I suspected!

We did not realize how close the bottom of the toilet was to the tank bottom. Apparently paper was simply stacking up and created the full tank appearance. When I first opened the valve without the clear piece attached some fluids came out. Seemed like only a small amount. When we noticed that the toilet had material with a watery appearance we thought there was a jam at the drain and since nothing was coming out that the slide valve might be stuck and the handle had broken off of the slide. Hence, the panic button. Buying the dual flush valve allowed us to see what was or was not going on.

To make a long story short, I stuck a clean out wand down the toilet and loosened the pile of paper, filled the tank with water and drained it several times. Until we got clear water.

Thanks so much to everyone who took the time to respond to our crisis. It is great to know that such help is available to those of us that are fairly new to the "RVing" experience.
Happy trailering to all.

Sounds like your clog might be at the toilet and the tank is actually empty. I would hook up a clear fitting and then the drain hose to a dump valve. Then use the tongue jack or level blocks tilt the trailer so the valve is the low spot. Now open the valve and see what comes out. If it only trickles and stops leave the valve open send someone up on the roof with about a 1/2 gallon of water. Have them dump the water down the tank vent pipe while you watch the fitting. If the 1/2 gallon flows out of the valve then you know your tank is empty and you have a clog at the base of the toilet. If nothing comes out you have a valve clog and hopefully the addition of only 1/2 gallon of water will not cause a catastrophe.

I bought one of these after having a similar problem. Does help a lot and makes cleaning much easier:

Dual Flush Valve

They often have similar items at Wal Mart.

it sounds more like the pipe connecting the toilet to the tank is plugged and not the tank outlet itself…
if that’s the case push it through with a piece of plastic pipe…

Deauxboy wrote:
BTW I bought one of those dual flush devices just so I could see if anything is coming out. Put it on and opened the valve. About a pint of blue water made it.

If a pint of blue water came out, it's doubtful you have a full tank. If you had a full tank, the dilution should have made all water brown, unless you put 10 or 20 gallons of blue stuff in.

I was going to try and get a septic co to come suck it out. All closed here today. Since we are leaving tomorrow morn for home I was considering trying a heavy cable snake. Using Pc. of flex PVC as a guide. Failing that I will pull the trailer over to our local septic service and see if they can help out. With 300 miles of bumping around I am kinda hoping for the result you mentioned.

BTW I bought one of those dual flush devices just so I could see if anything is coming out. Put it on and opened the valve. About a pint of blue water made it.

I want to thank all for the great input for our problem. This battle isn't over yet!

I'll post results of our adventure as they come about.
Thanks again

If the valve is opening now and nothing is coming out and your sure the tank is full but can not break it free you can try hooking the TT up to the TV and do a couple laps around the park doing a couple hard stops to move things around in the tank. Might break it loose if its a paper clog.

Time for a snake
The clog may only be in the toilet

You're right about the gauge. But when you open the toilet valve to flush the tank contents are actually coming up into the lower section. Looks full to me.

Given that the sensors are very inaccurate, how did you determine that the tank is full?

Try filling the bowl about 1/3 full and flushing. Does the toilet burp? If not, you're probably not full.

Do you have a clear adapter at the end of your sewer pipe? If the tank isn't full I'd try adding more water through the toilet and watch the adapter. If you just have a trickle coming through, it's just a matter of time before the clog disintegrates enough to push through. The added water weight behind it (in the tank) should help to push it through.

I'd leave the black tank valve open until you figure out if that's another problem. You can always shoot water down the toilet with a hose to clear things out.