I live in the middle apartment of a single level townhouse built in a straight configuration. The building is two years old and is on city sewer.
The bathroom is located against the south wall and contains the toilet, bathtub, and washer/dryer. The associated sink is in the hall just outside the bathroom. The kitchen is against the north wall.
When the washer starts the drain cycle, the water in the toilet bowl sometimes starts a wave action and/or bubbles. This morning, while the washer was in the drain mode I flushed the toilet and the water level in the bowl started rising to the overflow level.
There is only one 4 or 5 inch pvc vent line going through the roof. I looked in the attic and it seems that there is one pvc vent line coming from above the washer (horizontally - laying on the trusses) and one pvc vent line coming from above the kitchen sink. These two lines meet halfway between at a tee and go up through the roof.
I also opened the access in the front yard and ran a snake both ways and found nothing. I also ran a snake down the toilet and found nothing.
The water flow while the washer is draining and/or the toilet is flushing looks normal (through the access opening).
Thanks for any helpful information !
Cleo2

Hi Cleo,
The plumber revented all the vents back in the attic to just one main vent going out the roof. This makes it hard on the next plumber that has to snake a certain vent. You have a partial clog in the washer drain line and to snake it out you must go up in the attic and determine which is the lavatory vent and cut it free and snake from the attic. Afterwards he has to couple the vent back again. This is a job for a experienced plumber. Let him know what's up in the attic before he climbs up on the roof. Good luck, Tom