: Ensure you are using a flange plunger (one with an extended rubber lip) rather than a standard cup plunger meant for sinks.

If the blockage persists after utilizing a closet auger, or if sewage begins backing up into showers or sinks, the issue is likely located in the main sewer line (lateral). This requires professional-grade rodding equipment or camera inspection. Do not use consumer-grade drain acids, as these can damage porcelain and older pipes.