grinder pump holding case

Chopper and grinder pumps are similar in design in that they both have a mechanism to macerate any solids present in the fluid, but they differ in their primary uses. Here, we look at these pumps and their differences.

Chopper pumps

Chopper pumps are a centrifugal type pump that moves solids-laden fluid through a pumping system by using a cutting mechanism made from hardened materials that chops and macerates any solids in the fluid. The fluid moves into the inlet of the impeller where it passes through the cutting mechanism in order to ensure any solids are small enough to be handled by the impeller.

These pumps come in a number of different configurations – including horizontal end suction, self-priming, vertical sump and submersible pump – and many have a cutter at the back side of the impeller and may include a filter at the pump inlet to block any solids that are too large. 

Chopper pumps are typically owned and operated by private companies and are designed for specific industrial and agricultural applications such as for pumping manure, and processing waste. While they can be used in wastewater treatment, this is not their primary use.

These pumps are larger than grinder pumps so they are capable of cutting up very large solids such as bones which cannot pass through normal centrifugal pumps.

Grinder pumps

Grinder pumps can be either centrifugal or positive displacement type pumps, with both types containing a grinding mechanism as part of the impeller or rotor to grind the fluid before it goes through the pump.

Centrifugal type grinder pumps are submersible pumps where the motor, which is submerged in the fluid being pumped, is attached to an impeller with grinding teeth on the front and back sides. This impeller grinds any solids in the fluid before passing it through the pump volute to build pressure.

Positive displacement type grinder pumps on the other hand don’t have an impeller. Instead they have a submersible motor which drives a progressive cavity type rotors as it moves inside its stator.

Unlike chopper pumps which tend to be used in private industrial and agricultural applications, grinder pumps are generally owned by private individuals or small communities and used in municipal sewage systems to reduce the size of sewage lines and transport the sewage to a collection site or treatment plant. These pumps can be found in commercial buildings, individual households or a group of houses.

The main advantage of these pumps is that the sewage can be transported via pressure to a central point rather than gravity where homes are in remote locations or areas where the topography is not conducive for gravity systems. Furthermore, as the sewage line can be smaller (around 1.5 inches) where grinder pumps are used – compared to 4-6 inches for gravity sewer lines – the infrastructure cost is cheaper.

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