About 2 weeks ago, I noticed that the toilet would bubble and, eventually, the water would back up into the shower in the basement of my duplex down condo. What started out as about 12-15 minutes of time to back up (like the length of the shower), turned into a back up within 3-5 minutes.
Last night I used a bottle of Liquid Plumber in the shower, to no affect.
I'm certain that the sink, shower, and toilet are on the same line out, but after showering in a different bathroom this morning, it looks like this is not adding to the backup. My thought here is that this is a clog between the shower and the toilet, or down line from the toilet, and not a venting problem, since it's not affecting the other sinks in the house. Since I'm in Chicago, this isn't a septic issue.
I also believe this line is below the water line and feeds the sump pump. I'm investigating the sump tonight.
Any guidance or other thoughts? Anything someone might consider or had epxerience with?