17+ Bathroom Sink Overflow Drain Smell Pics. It seems to be strongest there, maybe because it's a natural vent. Bathroom sinks can begin to smell unpleasant when toothpaste, hair, and other items collect in the drain.
Without air behind water, a drain won't. Why the shower drain gets smelly. The fact is, the main function of those ports isn't as overflow drains, but as drain vents.
It has something to do with what goes down the drain.
An overflow is an optional feature found in some bathroom sinks. An overflow is an optional feature found in some bathroom sinks. I have tried running bleach through the hole which lots of black gunk came out, but the smell still returns. I think the brush needs to be longer to really do the job.