I'm on public sewer, and I have a toilet that has started bubbling occasionally. The toilet has never had any drainage issues prior to this. I read online that a blockage in the air vent was a likely culprit. I tried snaking out the vent on the roof with a garden hose. No apparent result. Then I ran water down the vent, expecting that a build-up of water behind a blockage could be heavy enough to clear it. The result was a flood in the bathroom and a newly backed-up toilet. Plunging did nothing, very warm water helped but didn't solve the problem, but some sulfuric acid down the toilet got it flushing nicely again. (I hate using chemicals, but I guess I hate a non-functioning bathroom more.) While I was cleaning the bathroom back up, I noticed that draining the tub got me more toilet bubbles, and the tub now drains slowly. Uh oh. I'm thinking I need to snake down the tub overflow drain, but I can't figure out how to get access since it's held in not just by screws but by the drain stopper mechanism. Am I headed in the right direction here? I'm wanting a really simple solution like pouring boiling water down the tub drain, which I figure I'll try while I wait for your helpful suggestions. Thanks!
Update: Toilet is draining slowly again with nothing more than cleaner and water flushed. :( When plunging, I hear noise in the tub drain, but otherwise get no results.