What would cause a sewer type odor in your bathroom when running the washing machine on the other end of the house, there is not an odor any other time, just when doing the laundry? We are on a septic system.

You are getting back pressure from somewhere. The washer pump discharges with great force. If it hits a obstruction it will set up a back pressure sending a bubble of sewer gas ahead of it. While the toilet bowl and wax ring's designed to prevent water from leaking when the toilet's flushed it isn't designed to prevent water and gas from leaking out when they back up. The first thing I would have checked is the septic tank. If it isn't vented you might wish to install a septic tank vent so he sewer gas vents into the air and not your house. If the septic tank appears to be OK then I would snake the drain from the washer roof vent or the washer standpipe.
Good luck, Tom