WE are at a total loss, I hope someone has some suggestions. WE have a winter home that we rent out. For the past 5 years, we have had complaints about a sewer smell, when the furnace comes on. WE have had a new vent pipe added out side, all traps, have been checked and re checked, we have a new furnance. 5 years ago, we did add a washing machine and a dishwasher. We have had numberous plumbers in checking the piping that was done for the washing machine and the dishwasher is a mobile one that sits idle unless it is in use. Any suggestions would be GREATLY appreciated, we are at our wits end!