Effluent filter
A screen on a septic tank's outlet that keeps solids out of the drain field.
Many modern septic tanks have an effluent filter on the outlet tee that catches stray solids before liquid flows to the drain field. It should be rinsed clean at every [pumping](/guides/septic-tank-pumping-cost); a clogged filter can cause slow drains or backups, while a missing or damaged one lets solids reach — and ruin — the drain field. Cleaning it is cheap insurance against a five-figure repair.