I have a sewer smell in my main bathroom coming from the sink not the shower or toilet. It only happens when I run water in the sink. I have had the vent pipe on the roof checked and I had a plumber here and he did not know what it could be but he wanted to start with the wax ring on the toilet. I have asked around to a lot of people, plumbers, handymen, etc. I had my whole bathroom remodeled many years ago and this is when it seems to have started. I am lost and don't know what to do next. Any help?

Is your drain , waste, and vent system connected to a sanitary sewer, or a private septic system? Have you opened the main drain cleanout, and sniffed to see if the odor there matches the odor in the bathroom? Have your plumber perform a peppermint test on the dwv system / piping, this will determine if the odor is in fact a leak in your drain or vent piping, and, tracking a peppermint odor trail can be easier and definitely more pleasant...

Thanks. I will get someone to try that for me.