A rancid odor coming from your sink drain may just be coming from debris in the P-trap, but if it smells like a sewer, it probably means venting problems in your drain system. When the vents are blocked, flushing a toilet can create sufficient vacuum to suck water out of the trap and allow sewer gases into your home.,
Baking Soda and Vinegar While your water is heating, pour one cup of baking soda and one cup of vinegar down your drain, and let the mixture sit. After about ten minutes, flush the drain with boiling water. Finish up by flushing the drain with cold tap water, and wait to see if the odor is gone.Jun 28, 2021
If the P-trap isn't working properly, sewer gasses can make their way into the bathroom and cause your sink to stink. Your sink should also have a vent that gives backflowing gases somewhere to go. If the sewer smell in your sink is caused by a blocked air vent, you may need professional assistance.