I live in a 2 story townhome. The master bathroom and a 2nd bathroom are upstairs, and there is a guest bath downstairs. On Friday, the master shower would not drain properly. The toilet also was backed up. THe other bathrooms are draining fine. I have tried baking soda and vinegar, drano, a 20" snake and sulfuric acid. Nothing is working. The toilet and shower back up, then after and hour or two will be back to a low level, so something is getting through. Anyone have an idea what the problem might be and what I can do to fix it? Or am I stuck and have to call a plumber? Thanks