sewer gas

Thanks for all the info. We upgraded from a 2002 CC 35RLS tag-a-long, to a 2010 CC 36RE fiver about 3 weeks ago. We could go for ALMOST a month before dumping the 35RLS black water tank with NO problems, no gas bubble.
I suppose I'm just used to that frequency. The 36RE only lasts for a week +, before the bubble forms.
A fellow camper had the same issue with his Cameo. He flushed out thru the vent stack and the problem seemed to disappear. Think I'll try that and see if there's some blockage??
Steve

I would suggest that you purchase about five pounds of ice, drop it in the black tank via the toilet. Add enough water to fill drain pipe from valve to the tank. Then go for a drive making lots of turns. The ice with slosh around and break up poop and other things. Once you have been out long enough to allow the ice to break up the sludge, fill the tank with water and dump. Amazing to find allof the stuff that makes it into a black tank. Ses if this helps.

search for poop pyramid and run that possibility down first before you start dragging stuff up on the roof.

My thought anyway.

Mine also burbs when it is getting full. It may just be that the tank fluid level is above the vent pipe inside the tank. Naturally that would impair the venting. I suspect most installers would install the pipe in the tank a little farther than we would prefer. As a solution, I do not flush with the tank near full, while sitting on the toilet. :)

Some folks,us included,take that "burp" as a signal that it's about time to drain the tank.The readings on the sensor inicator are not what we can call trustworthy!
BTW,be carefull about pulling the vent pipe up. Mine is sealed in place with
a big glob of "something" at the tank If you pull up on the pipe it will break the seal or possibly pull it out of the tank completly.Then you'll a BIG problem.

That may be normal. When the black tank approaches the full mark a bubble will form for a moment at the toilet valve before bursting and releasing its gas. In my previous RV when the bubble formed it always indicated the tank was approaching full and time to dump. I haven't noticed that in my current RV, however, but it's probably because I never let the tank get too full.

Toilet 'burping' when you flush after tank has been in use for couple days......
As fluids go into tank air is displaced thru vent.......as fluids drain out of tank air reenters via vent.
When vent is blocked air escapes via toilet when flushed.

That sounds like vent pipe is too far down into tank....either cut too long or has dropped down. Tanks are pretty shallow so if vent line sticks too far into tank it will get blocked as level in tank rises.

Go up on roof....remove vent cap for black tank and check location of vent pipe.
Should be level with roof line or just slightly above.
Run water down thru vent pipe with a garden hose.

If top of pipe has dropped....pull it back up and then strap it in place (if you can find access to pipe run)

If pipe was installed too long then will need to drop tank, cut off excess and reinstall......no fun!