Unusual Black Tank issue

[Kkeith1961]

Hello All. I'm new to the forum and new to owning a Redwood 4001LK, but it's not my first fifth wheel.

I think that there is a problem with the vent line for the front toilet in the unit. When you flush the toilet, as the valve opens, we are getting air bubbles back up through the toilet.

Has anyone ever experienced this, or something similar, and if so, what was the issue?

Thanks.

Follow up: So...the waste finally backed up into the toilet but didn't overflow last night. I completely drained all the tanks, and I used the sanitation rinse . The tanks appear to be empty, but there is still water standing in the toilet pipe just below the flush valve, as if the line were clogged between the toilet valve and the tank.

[XCMARK]

our toilet as the tank get close to full burps but only if there is less then 5~8 gallons of room left in the tank. My guess is your have a hard cone of TP/poop built up where the toilet dumps into the tank. only good way to remove it is with a hose down the toilet . Make sure you pre-charge the tank with 10 gallons of water and dump and rinse the tank only when its needed, NEVER LEAVE THE TANK DUMP VALVE OPEN! When you tow the camper add the same 10 gallons of water with a little dish washer soap also help. Good luck

If all else fails measure the length of pipe from the floor of the bath room to the top of the tank then measure the inside length of the pipe, it should be within 2" of the outside. If it's into the tank to far it will cause the issue your having.