Sewer smells cannot only be nasty, but they can create headaches and other health issues. Some of these things can be rectified by the home owner without additional cost. Every drain in your home has a trap. It is U-shaped in order to hold water to keep methane gas from getting into your home. Check any drain that is not getting water on a regular basis, and pour a cup or two of water in the drain and allow time for the smell to go away. At the base of a toilet, you can hold a flame from a lighter near the base of it where it meets the floor. If it is not sealed properly, the flame will either blow away or suck in. If this happens, you know you have a sewer gas leak under your toilet. Inspect your home for any pipes that have had a fixture removed and has not been capped off. If not, there could be other causes like a nail or screw put into a wall that peirced the vent pipe. This can be determined by a smoke test. If you have done all these things and still have not resolved the issue, please contact fullnelsoninc.com/contact. We hope this information has been helpful!