Plumbing – Why is the kitchen island sink gurgling when the dishwasher is draining

You may want to check to see if the sewer line vent pipe(s) that go up through your roof are plugged up. A plugged vent line cap prevent proper sewage water flow in the drain lines.

The foul smell in and around the bedroom area could also be caused by a plugged vent pipe that is keeping sewer gasses from dispersing in the proper way.

It it is a new build, then removing the trap under the sink will not be an issue. Just loosen the nuts, remove the trap (have a pan underneath) and then clean the trap. This is most likely the source of the slow draining. If the trap looks clean, then get a hand auger (snake) to clean the drain line. It is best to do this with the trap out. Hand augers are typically half the cost of a plumber call. If it is still slow, then your drain vent might be clogged. At this point, it is usually cost effective to call a plumber to clear the line.