My house is only one year old. There is a sewage smell coming from the drain everytime I turn the bathroom faucets on. It is not the water that smells. It is a blast of air that smells. I have taken the PVC pea traps out and replaced with metal traps. Plumber has been out several time and can't figure out why it is smelling. Vent pipe is open. I have run bleach through the drain and through the overflow. It is a marble counter top and sink. Basically I have tried everything with no success. I can only trust the plumber is giving me the right information. I am on city sewer pipes and not septic tank. Help Please