To determine if your P-trap is clogged and needs cleaning, look for these signs: Slow Drainage: If your garbage disposal drains more slowly than usual, I bet the P-trap gets partially clogged. Water Backups: If water is backing up into the sink, it indicates there may be a blockage in the drain line, particularly in the P-trap. Gurgling Noises: You will hear a gurgling noise when the disposal drains, which indicates a possible clog in the P-trap.