Reversing Grinder Pump Excels in Pressure Sewer Systems

Over 11 years ago, when the Zoeller Co. introduced the reversible grinder pump, few would have predicted how successful the concept would become.

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Th 158161
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Over 11 years ago, when the Zoeller Co. introduced the reversible grinder pump, few would have predicted how successful the concept would become. During the 80s, as the company observed the growth and acceptance of the pressure sewer concept, there was little doubt that their customers would eventually require a grinder pump.

But, during market research, one common complaint about grinder pumps was consistently heard. It was said that after a few years of service, the cutter blades began to dull, clogs would begin to occur and eventually jam the pump. The unit would then have to be removed from the basin for service. These service calls and system shut downs were a major nuisance. The engineers at Zoeller set out to design a grinder pump that would not jam.

The idea for the reversible grinder pump was inspired by a reversing cutter blade successfully used on some garbage disposal designs. The question was, could a pump be designed that would operate in both the clockwise and counter-clockwise direction? Working with their component suppliers, Zoeller engineers determined that it was possible. This led to the quest for a wet-end design that would enable the impeller to pump the same amount of liquid while drawing the same amps regardless of which direction it was turning.

Through trial and error the engineers, assisted by machinist in the Zoeller R&D department, developed a reversible grinder pump featuring a star shaped cutter blade. The cutter rotates across a stationary flat plate. As the sewage is pulled through the orifices in the plate, it has to pass the star cutter, which turns 57 revolutions per second.

When used with a control panel incorporating a special reversing module, the pump is instructed to turn in one direction during a duty cycle and then instructed to turn in the opposite direction for the next duty cycle.

Zoeller sold its first 2 hp grinder pump in 1993, even though the reversible grinder pump was initially met with skepticism. Since then, sales of the product has increased every year. A few years ago, the company expanded its range of reversing grinder pumps to include 3, 5, and 7.5 hp units.

The cutter design has provided some unexpected results. The shearing action of the rotating star cutter across a stationary plate has proven to be a very dependable cutter mechanism when used in a single directional grinder pump. The success of the cutter is related to its ability to remain sharp over time. The stainless steel cutter and plate material is hardened to Rockwell C55-60.

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