SaniTEE® screens work as sewage enters the septic tank, grease, oils and light weight particles rise to join the scum layer at the water surface. Heavier solids settle to the bottom to join the sludge layer. In between these layers is a zone of relatively clean effluent. This effluent enters the side of the SaniTEE® screen, passing through the angled slots. Clarified effluent then travels up through the inside of SaniTEE and out through patented keyhole weirs to discharge via the standard outlet piping. As solids come in contact with the smooth vertical surface of the screen, they tend to slough off, falling back into the septic tank, instead of collecting inside the filter housing.