We started to get an eye watering stink in the bathroom that wasn't gifted by us. It seemed to be coming from the cabinet under the sink. John took apart the sink drain trap and cleaned it but the stink persisted. I tried to pull apart the vent pipe under there but couldn't get it.
A Google search showed that vent is called a "cheater" vent, used when you can't tie into an outside/roof vent. The proper plumbing term is "air admittance valve". The purpose of the vent is to allow air to enter the system as water drains thereby avoiding a vacuum. The pull of that draining water opens the valve, lets in air, then a spring or diaphragm device closes it again so sewer gas doesn't roll in and stink up the house.
I put a plastic bag over the vent and twist tied the bottom to see if that was the cause. YES! No more stink. This likely means the vent is stuck open.
Further internet searching says to spray lubricant into the hole on the top of the vent to loosen the stuck spring. That's my next move, once I figure out how to get the spray into that tight space. If that doesn't work, we have to replace the valve (or live with the plastic bag and potential sink gurgling.).
