by Why does my toilet water rise unusually high before flushing?
Short Answer: A downstream restriction may be slowing wastewater movement.
Detailed Answer: When the drainage path is partially blocked, water may rise higher than normal before eventually flushing or draining slowly. If multiple fixtures show related symptoms, septic or sewer-line restrictions should be investigated.
Related Questions: Why does toilet water level change? How do I diagnose drainage restrictions? Can septic problems affect toilet performance?