The tub is clogged and fills up when using the sink
It's not uncommon for debris to build up in a bathtub's siphon and clog the drain . However, if the tub backs up when you pour water into the sink, you can be sure that the tub's trap is unclogged. It's obvious that there's a clog, but it's past the point where the sink and tub drains converge. There are several ways to clear the clog. If one doesn't work, try another. Assess the situation Soap scum, hair and other debris can easily clog a bathtub drain, and the clog grows the slower the water flows and the more debris can settle. If you don't know where the clog is, the bathtub drain is usually a good place to start looking, but not if water from the sink is backing up into the tub. This backflow is a sign that the trap is unclogged. The clog is likely several feet from the drain, so you can't reach it with a snake inserted into the drain opening - usually a reliable strategy. Immersing the tub For the plunger to have the greatest effect, ...