The upstairs bathroom in my house has a sewer smell and the smell is only in that bathroom. The bathroom is not used everyday, but at least several times a month. There are no signs of leaking on the bathtub, sink or toilet. A plumber came today and told me the vent stack on my roof is too close to the non-opening skylight in this bathroom. He said the sewer smell from the vent stack is coming back into the bathroom through the non-opening skylight. He suggested I have the vent stack moved to another location on the roof. We have lived here for more than 20 years and have never had this order problem before the last couple of weeks. Is this plumber right? Or is there something else we can try?:confused:

Smells are hard to track down. Start with the traps in the sink and tub. Make sure they're full of water and cleaned out - no hair, soap, grease, etc.

If that doesn't do it, the wax gasket under your toilet might have failed letting sewer gas out into the room.

Your plumber isn't much of a roofer. How does he explain sewer gas coming through a skylight that does not open? He is full of beans on this fix, ignore him in the future. The vent stack is a likely candidate but not because of its proximity to a non opening window. Did he suggest the wax ring on the toilet, I sure would start there.