A couple of weeks ago, I started having problems with my toilet flushing properly. It seemed to be a clog so I used a plunger. That didn't work. Draining water from the sink or tub causes the water level to rise slightly for a few seconds then it starts to gurgle (not bubble). The water from the tub and sink drains completely and the toilet bowl water level returns to normal. Am I looking at a clogged vent pipe or partially clogged drainpipe?

Thanks.

Gurgles indicate a blocked vent while bubbles indicate a partial clog. Snake the roof vent, Put out enough snake to reach the base and 16 more feet. Good luck, Tom