After taking a shower in the upstairs bathroom we get a sewage smell down stairs. I have checked all drains for the smell but have been unable to locate where it is coming from. Where or what else can I check?

What seems to be happening is when you take that shower upstairs and while that water is draining it needs to draw air from the rest of the drainage system in order to drain and not vacuum lock. That air is supposed to come from the plumbing vent. However if that vent is blocked and or frozen with snow the water going down that shower drain is siphoning air from the rest of the house drainage and that will cause you losing water in the downstairs sink trap that block sewer gas.

So if its not a frozen /clogged vent pipe the vent pipe itself may not installed properly causing that siphonage from downstairs sink

Hi Shoop

Is this a new issue or has this been an issue since you moved in? Let us know...

Mark

This should be left up to experienced and trained technicians to do the sewage cleanup. A professional company will be able to conduct the sewage cleanup in a safe manner.

Shoop is talking about a sewer SMELL SpaParts, not a sewage spill...;)

And since there is no sewer spill I won't go into details about cleaning things up, but it doesn't always require a professional, for sure!!