sewer smell

We recently added a laundry room to the garden level of our house. A few months following this job we started noticing a sewer smell in the laundry room when the top floor shower is used. The plumber insists that he hooked up the laundry to our vent. What could be causing this? There is no smell when the laundry, garden floor bath or kitchen are used.

By dt | 02/03/2008 8:59 AM