I have a sink that when the water is first turned on you get a sewer gas smell that comes from the overflow hole in the sink. You can also feel air along with the smell coming out of the overflow. I have checked the vent pipe going to the roof and it is clear. I replaced and lowered the existing p trap under the sink thinking I would get more water in the trap for a better seal. I was thinking of placing another p trap in the 11/2" drain pipe that runs to the 4" main drain right where it tees with the vent pipe. My questions are: Can I just splice this trap into the existing drain and have both ends of the p trap at the same level, or does one side of the trap need to be higher than the other? Will this solve my problem? Thanks

iamgrowler

You do not want to add another trap, what you're smelling is likely rancid soap scum, hair and tallow sticking to the inside of the overflow chamber.

Stopper the sink, boil enough water on the stove to reach the overflow and then a gallon or so more to loosen things up, and then pour a gallon of bleach into the sink before unstoppering it.

sam4912

The sink is new, so I don't think the smell is coming from the overflow. But that is when we noticed the smell, after the install. I did pour bleach down the drain, let it sit overnight and then poured about 2 gal. of boiling water down it in the morning. It killed the smell for awhile but returned later. Should there be air coming out of the overflow when the water starts down the drain? Also the drain to this sink connects to the vent pipe going to the roof. Is that an approved connection? Thanks for the reply.