I have a new 2011 Landmark Augusta and ever since we have owned it the black water tank builds up pressure in the tank, this is when using it when it get about 2/3 full it will plow back into the stool, also when flushing if the tank is closed off it builds up pressure they say not to close off tank when flushing but how do you get the tank full to do a good flushing the gauge alway says full no matter what:angel:
Jim, help me understand what you mean when you say "close off tank when flushing". All of the replies so far are possible but what you are experiencing may be normal depending on the severity of what you mean by plow back into the stool.
First, your gauge will read 2/3 until the liquid level reaches the full sensor. It will actually read full almost always after a flush because of splashing going on down there. If you are getting a "big bubble" when you flush, that's normal. If you are getting liquid and brown water, you have a problem down there.
If in the past, IF you have kept your black tank valve open when you are hooked up to a sewer, that is the wrong thing to do. This allows the liquids to drain but the solids and paper build up in the tank directly under the pipe from the stool. Eventually, it will block passage of everything.
As said before, other possibilities are a blocked vent pipe or the main drain has come loose and slipped into the tank. You might try one of those sprayer hoses that you can stick down the stool and make sure you don't have that "pile of pucky". If you do, it should break up with that spray tool.