Orenco’s Biotube® effluent filters prevent the discharge of large solids from the tank, dramatically improving the quality of effluent and extending drain-field life. Effluent from the relatively clear zone of the Septic Tank, between the scum and sludge layers, enters the Biotube effluent filter through its vertical inlet holes. Larger practices are retained in the interior space, where further decomposition of organic materials occurs. Optional flow modulating orifices at the outlet of the filter slow the flow through the tank, allowing maximum settling of solids.