Recently our downstair bathub has started burping while it drains. Seems to drain OK, but the burp, burp, burp while it's draining has me a bit suspicious. We are on sewer system, there is no bathroom above this one (although I'm not positive how the venting works). I've snaked this a little bit, but no effect, and it does seem to drain OK. I'm guessing my next stop is the roof vents for an inspection, at least.

Should I be concerned about this?

Thanks!

Your tub's venting through the tub waste and overflow. This points to a blocked vent. You were correct. Be careful up there. Tom

I have a sink that 'burps' about ten seconds after the drain empties. Seems like it's a vent problem but I found no obstruction in the vent. The same vent services the tub drain which does not burp.