: I live in a bottom floor unit of a condo bldg. Lately I've been noticing a fairly loud, deep dripping noise / rumbling in my tub/shower. It sounds like it's behind the wall. There is no water actually dripping in the tub. It's a shower/tub that is not used very often - could that have anything to do with it??? Someone said something about "air pockets" or "gas pressure" build up?? Any ideas for diagnosis and/or repair. It doesn't do it at any particular time that I notice. It's not all the time, but it's everyday. Thanks!