[LazyPup]

Low water level is a prime indicator of an obstructed vent. To locate the vent look on the roof of the house directly above the bathroom area, you should see a 3 or 4 inch diameter pipe sticking up through the roof about two feet. If you have a basement go down and look for the wetvent stack directly below the vent pipe on the roof. There should be a cleanout cap on the base of the vent stack where it meets the building drain. You can either snake up from the bottom or if your on a slab it is easier to snake from the top down.