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