[Stormieweather]

<< Real Estate Pro here. Put the problem(s) in writing, take photos, and mail it certified, return receipt requested. Ask for immediate resolution. Check online for legal notice periods for tenants and landlords (they vary by state). Give him that period of time before you start threatening legal stuff.

Before I got to this last picture, I was guessing blocked sewer vent. If that sucker is blocked, for whatever reason (and I also mean the one out the roof), it can fubar your entire drainage system. I had a 90 year old house (lots of DIY repairs by previous owners) and the underground sewer pipes were full of roots and they sort of neglected to put in an air vent for the added on bathroom downstairs. Oh the heartache, backache and headache figuring that out gave me. The picture and your plumber confirmed my thoughts.