Our bathroom was remodeled probably around 9 months ago or so. All plumbing used was HVAC. We moved the sink and the toilet drain and connected them back into the larger house drain. I notice that over time a smell comes from the sink drain. More noticeable if you're bent down washing your face or something. I've had some success with using lye as a drain cleaner. I'm guessing something is not quite plumbed right and I'm basically smelling buildup in the catch or something. Is there a drain cleaner that I should use? Liquid or perhaps motorized or something? Thanks!