I have two full baths on the top floor, a half bath and kitchen (w/dishwasher) on the middle, and a laundry sink and clothes washer in the basement.
All have "P" traps, all are used daily so that water stays in tne "P" traps.
This sound just started happening about 4 months ago, and ONLY in one of the bathrooms on the top floor. The house just turned 3 years old.
I imagine that all the plumbing is vented in the same pipe? Is the vent pipe clogged? If so, wouldn't all of them make noise?
I've tried the chemical cleaner in the sink thinking a "hair clog"....but no dice.
I'd love any suggestions!