Not all grinder pumps are created equal. E/One's grinder pump lends itself to complex system designs because of its nearly vertical pump curve and the resulting nearly identical flow rate allows a wide variety of discharge heads. The predictable flows of the semi-positive displacement (SPD) pumps provide tolerance of widely varying system pressures.
The use of SPD grinder pumps is crucial to the success of a pressure sewer system. The performance characteristics of SPD pumps assist in maintaining a sewer network free from blockages. When deposition of solids occurs, tending to block the pipe, centrifugal pumps will move toward shut off, reducing flow and velocity and increasing the tendency to block the pipe. SPD pumps constantly scour the lines to prevent buildup because flow is maintained although pressure or head increased, effectively scouring the pipe.
Pumps & Systems magazine published an article that explores why SPD pumps are a better choice for sewer systems.