A septic tank is an underground tank that provides primary settlement and partial biological treatment of sewage from properties that are not connected to a public sewer. Solids settle to the base as sludge while lighter material forms a scum layer on top, and partially treated effluent passes through a baffle into a soakaway or drainage field for further treatment in the soil. UK installations must comply with the General Binding Rules for Small Sewage Discharges issued by the Environment Agency, as well as Building Regulations Part H2 and BS 6297. Direct discharge of septic tank effluent to a watercourse has not been permitted since 2020, so older systems may need upgrading to a package treatment plant. Regular desludging, typically annually, is essential to maintain treatment performance.
Septic tank
Underground tank that partially treats sewage where no public sewer connection is available.
