Sewer line runs below slab and has about 1/8" per foot slope. Main line has been photographed and is clean. Line has clean out, lav, Studor vent, toilet (Toto). Branch with washer and laundry sink connects below that. Line connects to larger line with proper slope. Everything has been fine for about 18 months. Toilet over flowed during a party. Toilet was plunged, and snaked. Toilet over flowed, then drained very slowly. Main line was snaked and photographed. Toilet over flowed then drained very slowly. Water backed up through clean out. Second Studor vent was installed at laundry sink. Today, toilet would not drain properly, then drained very slowly. Water backed up through clean out and was apparently forced out through wax ring. Any suggestions?
Tom Baker