Water sometimes come up in the tub, but the drain is not clogged.I in a condo on first floor of 14 story high rise

bathtub

Dirty water backs up in my tub sometimes,but my drain is not clogged.I live in a condo on the first floor in a 14 story high rise

Best Answer

Clearly your drain is clogged, but below where your sink joins the main drain; it is not fully blocked however.

If enough people run their sinks/whatever hits that line, it fills up and backs up, and eventually it will hit your sink.