A Septic Tank System (STS) is the most common type of wastewater disposal system for small village houses in areas where no communal sewer is available.
A STS can only perform well if it has been properly sited, designed, constructed, used, desludged and repaired when necessary.
A proper wastewater disposal system (including STS) should be installed for the disposal of both toilet waste and sullage (i.e. wastewater from shower and sink etc.). See diagram below. Disposal of sullage into surface channels can be tolerated only if this does not result in pollution. Where necessary, the Environmental Protection Department (EPD) may require the responsible householder to install proper facilities (e.g. a STS) for the disposal of toilet waste and sullage. Pollution associated with the incorrect disposal of wastewater can result in prosecution under the Water Pollution Control Ordinance.