As used in this chapter, certain terms are defined as follows:
(1) “BOD” or “biochemical oxygen demand” means the quantity of oxygen utilized in the biochemical oxidation of organic matter under standard laboratory procedures as prescribed in “Standard Methods for the Examination of Water and Wastewater” in five days at 20 degrees Centigrade, expressed in milligrams per liter.
(2) “Building drain” means that part of the lowest horizontal piping of a drainage system which receives the discharge from soil, waste and other drainage pipes inside the walls of the building and conveys it to the building sewer, beginning five feet (1.5 meters) outside the inner face of the building wall.
(3) “Combined sewer” means a sewer intended to receive both wastewater and storm or surface water.