I was hoping someone here could help.
I've got a 2014 XLR 415AMP. One, 100gal, black tank, 2 toilets. The rear toilet is working fine. The front toilet "burps" when you flush it. It also seems to build up pressure when the flush ball is closed. My toilet is a Thetford 42072.
I've checked all the roof vents and they're all open. Dropped a snake into the holding tanks from the top and no obstructions found.
Checked the plumbing visually and found nothing "weird". Only 2 elbows used in the install and both were, IIRC, 22 1/2. Waste pipe is clear.
I called my dealer. He says it's most likely a bad vent breaker on the toilet. I've got one on the way from Amazon. $25 won't bankrupt me if it's not the culprit.
Since my dealer has screwed up everything they have touched, I called Thetford. They say the vacuum breaker can't be the problem and that I should install a cheater vent in the lines to aid in venting. They tell me I probably have gas bubbles built up in my tank and they are escaping through the toilet. They stuck to this even when I told them the vent pipe is right beside the waste pipe and it's clear. They say the vacuum breaker actually has nothing to do with pressure/gas relief.
I've never heard of adding a cheater vent to a "waste" pipe. Sinks, yes, toilets, no...
Opinions? Suggestions? I'm running out of things to check.