Originally Posted by Yukon
Tank is pumped out. I'll check the vent.
Thanks so much
You may have been to the pumpout, but unless your tank level indicator shows the tank to be empty, it may still be full. Your symptoms indicate that to be highly likely. If so, it's not a VacuFlush problem, it's a holding tank problem.
The tank vent has two functions:
1. It's the escape route for air in the tank displaced by incoming waste. If air can't escape, the tank--the whole system-- becomes pressurized...increasingly pressurized as the toilet is used. Air in a pressured system will try to escape wherever it can...back through the toilet (count your blessings if it's only air and not a geyser!)...or in extreme cases, it'll blow out a hose connection or even explode a tank.
2. It provides a source of air to replace tank contents as the pumpout or overboard discharge pump pulls them out. When no air can come in, the pump can only pull out a gallon or two before it pulls a vacuum that won't allow it to remove any more. A particularly strong pumpout pulling against a blocked vent can even implode a tank.
So I strongly recommend that no one use the toilet again until you locate and cure the problem.