Sewer smell coming from under bathroom sink. The odor is so strong that it can be smelled alllover the house. Please help. Plumber suggested cuttting through drywall on back side to check connection. Is there a more exact way to determine what is causing the odor?

Truk 1987

First off we need a few more details. Where's the bathroom located? Can you see any moisture around the wall or floor line? Where is the smell worse? From the drain when you run water down it or is it strongest away from the drain and near the trap in the cabinet? Most bad smells from a lavatory come from hair built up on the plunger rod and decaying down there. Every time you open the stopper to drain the lavatory you get a nose full of stinky.
The first thing I would look at is the stopper. Pull it and you will find a pivot rod about 6" down in the drain,(see image). Shine a light down there and if you see a buildup of hair fish it out. If the stopper's tied down let me tell you how to free it up. Push down on the plumger so that the stopper pops up. Underneath the lavatory ahead of the clip you will see a knurled nut,(Leave the clip on)Now back the nut out until it's free but don't pull it all the way out. Now while you are pulling up on the stopper GENTLY pull the rod back until the stopper clears, stop! Now screw the nut back in place and just snug it up with a pair of pliers. When you clear the drain just drop the stopper back in. Some plumbers lock the stopper in when they install the fixture. I never have for it makes it impossible for the home owner to clean the drain. After you clean the hair pour a 1/2 gallon of bleach down the drain and let it set overnight without using it. Next morning flush it down with a pan full of boiling water. Good luck, Tom

Thank you for your suggestion. The house is very small. The bathroom is located down the hall with a closet that holds the washer a dryer. The smell is definitely coming from under the sink. The cut outs are over sized under the sink so I suspect this was a problem before we moved in. The plumber thinks that it's the drain coming from the toilet. He wants to cut out the wall behind the toilet and sink to see if a pipe is lose. I am hesitant to allow this because I don't think he can reach the problem from where is going to cut out the drywall.
Isn't there a little camera that can be fished through the sink opening that can look behind the wall before he starts cutting away the drywall.


Thanks for all your help









T