The most common reason for “sewer gas” smell in a bathroom is a deteriorated wax ring under the toilet. Other possible causes for this smell could be a broken or leaking p-trap under the shower or bath tub, or a leaking p-trap under a bathroom sink. One additional cause could be a build-up of hair in the sink drain mechanism that is decaying. While this is not technically sewer gas, the smell of decaying hair is remarkably similar to sewer gas and is often mistaken for this. This smell is the most easily remedied, as the solution is to clean the hair out of the trip lever mechanism.
If the smell is from the toilet, it will be necessary to pull the toilet up from the floor, remove the old wax ring, and install a new wax ring. New floor bolts should also be included in this repair; and a new shut off valve and toilet supply line are always a good idea. Then, caulking should be applied around the fixture to complete the repair. If the caulking is not done, air will get under the toilet and dry out the wax ring and cause it to shrink, putting you back at square one all over again.
If the cause is a broken or leaking p-trap, if it is under the sink, the repair requires a new p-trap to be installed. If the leaking p-trap is under the shower or bath tub, this is definitely a job for a professional as it will most likely require the removal of the shower or bath tub to make this repair.
At Sav-On Plumbing, we are qualified to diagnose the cause of the problem and to make the repair. Cal us for a free consulation on the cause of your sewer gas smell and a free estimate on the repair.