I recently had a basement bathroom finished by a contractor. I'm noticing a problem when the tub drains. First off, the tub drains super fast, I was initially impressed, as I've never seen a tub drain so fast. The whirlpool generated has at least an inch "eye", and it's quite noisy.
From what I recall during construction, the tub & vanity share the same 1 1/2" vent pipe that goes up into the second floor and out the house.
The odd thing happens when the last bit of water leaves the tub. It literally seems like the negative pressure in the pipes as the tub water drains empties the water from the P-trap in the vanity, this leaves me to hear the tub draining through the vanity, and I would also guess would allow sewer gases to escape up into the vanity.
I would like an expert opinion on whether I should approach my contractor to correct this. I've already paid him for the job, but he's remodeling the bathroom above this one, which may be part of the problem.