POWTS is an acronym for a Private Onsite Wastewater Treatment System. A more widely used term is 'septic system'. It is intended to treat domestic wastewater. The most common onsite system used is a septic tank in combination with a traditional drain field. A properly designed, installed, and maintained system should operate for 20 to 40 years or more, treating wastewater to minimize the negative impact on groundwater, surface water, and human health.