This standard contains minimum requirements for residential wastewater treatment systems having single, defined discharge points and rated treatment capacities between 1514 L/day (400 gal/day) and 5678 L/day (1500 gal/day). This standard was first adopted by the NSF Board of Trustees in November 1970, with a revision in 1978. This standard focuses on aerobic wastewater treatment plants for the treatment of wastewater from individual homes and other sources having similar types and volumes of liquid wastes. Disposal of treated effluent from these plants is not included in the scope of this standard. The following criteria are discussed: materials; design and construction; standard performance evaluation; effluent requirements; operation and maintenance; and safety. Also included in this standard are NSF policies relating to the use of NSF seal on individual aerobic wastewater treatment plants, inspection of facilities, records, reports, and sample collection, testing and test reports, and onsite inspection and service records.