Black tank problem

[skyviewman]

I posted a week or so ago about the black tank backing up. Someone said it might be the dreaded pyramid or else it might be the tank cutout that was left in the tank when mfg'd. We have only be using the toilet to pee and this last time it was only five days before it burped. After the tank is empty I usually pour a couple of buckets of water down the toilet and when I pour the first one down it fills the pipe and the toilet and paper in the pipe will usually float up. If I plunge it the water will go down and the second bucket goes down no problem.
I am at the point now where I am ready to take more drastic action and have a few questions and would appreciate any advice.
I don't have time to tackle it this year as we are due to return home and won't be back until next spring so what I am thinking of doing is to drain the tank and pour down 2 or 3 gallons of RV antifreeze for the winter. Next spring I will take off the belly pan and it looks as though the valve is on the bottom of the tank
My questions are,
If I take off the belly pan can the black tank valve be dismantled enough so that with a flashlight and a mirror I can see inside the tank to see if there is something in there fish around to break it up?
I know it would be a messy job but at this point I don't know what else to do.
Thanks in advance.

[SlickWillie]

So, do you have a tank flush system? What happens when you use it? If you use it, and the water backs up, the outlet is probably blocked. If it drains ok when flushing, I would suspect a pyramid or inlet obstruction. You could probably cut the 3" abs inlet pipe and look in there. Just re-connect using a rubber coupling (which is not bad anyway, as it allows movement without breakage.)

[snfexpress]

I agree with Will, break the problem down into discrete areas so that troubleshooting is easier.

If it is a pyramid, you might want to try using 5 Star Happy Camper's Extreme Cleaner.

We have used their regular product for a couple of years, now, and really like it.

What year is your model?

[skyviewman]

Ours is a 2008 3400RL. I do use the tank flush system and I usually let it run for 3 minutes and open the tank valve again. I can hear the water draining out. Today after using the flush system I poured a pail of water down the toilet and that is when it filled the pipe and the toilet and after plunging the water ran free. I thought that maybe it was a pyramid bit when I use a snake I never come up with anything. Does the pyramid usually occur directly under where the pipe goes into the tank and would I be better to cut the pipe in the basement and work from there?
thanks again