The most common cause of a sewer smell in the house is a dry P-Trap, a curved pipe that is intended to be full of water and acts as a seal to hold out sewer gas. Unused showers or utility floor drains are often the culprits due to evaporation of the water in the trap. Fill all drains with a gallon of water. This should solve the problem. If it persists, call Champion Plumbing for a more thorough diagnosis.