black tank wont drain

noteven wrote:
I have heard of an instance where the round piece of tank wall that was cut out for the valve with a circle saw got left in the tank.

I can attest that this DOES happen. About 3 years after buying my first RV (a Winnebago) in 2007, I was dumping at home using a FloJet macerator. I had a clear section so I could see when "stuff" stopped being rinsed out. Lo and behold, the circle of plastic that had been cut out of the black tank to attach the toilet dropped into the clear plastic connector.

My black tank drained much better after that.

Thanks for all the. Comments and ideas! I will let everyone know when I tackle the job Friday. Again thanks for all the ideas!

I have heard of an instance where the round piece of tank wall that was cut out for the valve with a circle saw got left in the tank. It would get washed into the valve, back up undissolved paper, and stop the flow. It was found by looking in the tank with a boroscope.

“Flushable” wipes aren’t for in a holding tank system.

2 meter wipes (using 2 m or 6 ft of azz wipe) per set is asking for trouble.

If the valve is manual you should feel the difference to how the gray valve operates if it is broken. If it feels like both valve slides are opening the same I would see if someone would look in the tank with a scope.

And until the OP comes back with more information, this thread is pure speculation.
Nothing like open ended questions to start a good discussion....

Dusty R wrote:
Look from under neath to see if the slide valve/gate is opening.

Curious. HOW would you be able to see that?????? The only thing visible is the steel rod that comes out and in. IF the steel rod has separated from the valve blade(very common on this type problem) there is nothing to see, unless you have a straight line of sight from the dump cap to that valve. To the OP, IF the rod has indeed separated from the blade AND you have enough room, I drill a 1/4 inch hole on the END(opposite the rod) in the middle of the valve body. Have a 1/4 rod handy and insert into the hole(a little sewage water will dribble out) and use that 1/4 dowel rod to push the blade OPEN and drain the tank. Once drained, flush and then replace the 3 inch valve. Doug

I was worried about that problem on my last trip. Nothing wanted to come out. I tried back filling, and that didn't help. Finally had the dump valve open, and dumped a 8 gallon water container into the toilet, which flushed everything out.

If that doesn't work, and you have matter in the holding tank, and it isn't a matter of the valve being broken, I'd consider trying some Rid-X.

Look from under neath to see if the slide valve/gate is opening.

The flush attachment at wallyworld works really good, and is reasonably priced. About $15.00. It also directs the stream straight back into the sewer pipe. Shoots about 25 feet.

You pulled gate valve “open”, nothing came out?
99.9% sounds like broken gate valve to me.
Start there.

OS !