I live in a ranch home on a slab. This problem started Sunday where the toilet in our second bathroom will begin to gurgle when taking a shower in the main bathroom. The toilet is fine any other time but after this happens it will back up when fushing. It will drain eventually and I can hear it doing so as well. I am not a plumber so I don't know how to explain it right, but the main bathroom is closer to the outside main line and the second bathroom is further back. I have read other postings but they all seem to be a little different than my issue. Is it a vent problem, or a blocked drain problem? Can regular liquid pipe cleaner work? Also, we got about 10in of snow the day before, not sure if that matters. Please help.