ABSTRACT
There are two types of pressure sewers, grinder pump systems and septic tank effluent pump (STEP) systems. The STEP system pressurization unit consists of a septic tank or interceptor tank, pump chamber, pump, and control system. Some equipment suppliers are packaging STEP systems; however, most designers have chosen to build the system using various specified components. The most commonly used pumps in STEP systems are the small centrifugal submersible effluent pumps. In addition, William Bowne has recommended that soil vent fields be used to assist the venting within STEP systems, although he also recommends that the designer be very careful concerning infiltration of groundwater. It is also recommended that intermediate pumping stations and air release valves in an effluent pressure sewer system be vented to an underground drainfield if the pumping station is located near residences.
