A trap holds the grease, it does not remove it
Fats, oils and grease cool and set. A grease trap or interceptor exists to catch them before they reach the sewer, but it only holds what it catches. Once it is full, the grease has nowhere to go but down the line, and the first signs show up on the kitchen floor: drains that run slow, water that backs up, and an odor that no amount of mopping fixes.
That is the failure a routine pump-out prevents. The same trap that backed up a restaurant last month runs quietly for years when it is emptied on time.
