All waste water from the Cal Poly campus is discharged to the City of San Luis Obispo's sewer collection and treatment system. Cal Poly, in partnership with the City of SLO, has invested capital funds to purchase a capacity share of the City's waste water treatment plant, and therefore receives a discounted rate for waste water.
While most commercial sewer customers (in absence of a sewer flow meter) are billed for sewer use as a percentage of their domestic water use, Cal Poly's sewer usage is measured by a state of the art ultrasonic flow meter and flume, which is calibrated twice a year. This ensures accuracy in billing and reporting, effluent sewage volumes and cost. Ongoing conservation efforts, such as installation of ultra low flow plumbing fixtures, have resulted in significant reductions in sewer volumes in spite of campus growth.