Sewage Grinder Pump

Sewage Grinder Pump

What is a sewage grinder pump?

A sewage grinder pump is a pump used to convey sewage and grind waste into fine slurry. Waste from household appliances that is bathtubs, toilets, and washing machines is conveyed through the pipes in the home into the grinder pump holding tank. When the sewage in the tank increases to a certain level, the pump turns on and grinds the waste into smaller particles and then pumps it to the main sewer system. Sewage grinder pumps are installed in the basement of the house or the yard. When the sewage grinder pump is installed in the yard, the tank needs to be kept deep enough to ensure that the pipes and sewage are well below the frost line otherwise it will start freeing if the pump is installed in cold climatic regions.

How does a sewage grinder pump work?

A sewage grinder pump is a pump that is designed with a grinder system at its inlet. This grinding system in the sewage grinder pump is meant for cutting larger fibers and particles into homogenous sewage mass. Cutting the large particles helps to ensure that the pump and pipes are free from clogging as well as ensuring that the piping system is reduced to a minimum. A sewage grinder pump is meant for a pipe system that has pipes with smaller diameters and the flow is generally lower. The sewage grinder pump is useful when transporting wastewater from remote areas such as from single houses. The sewage grinder pump should not be used for pumping wastewater that has high contents of sand.

Components of sewage grinder pump station

A sewage grinder pump once installed forms a station. The sewage grinder pump station is made up of a tank, alarm panel, and pump. For household use, the sewage grinder pump needs the power of around 1 hp to 2 hp. The sewage grinder pump is manufactured with a sensor that is a float switch, built on the pump or attached to the pump externally. The sensor level’s ability varies from pump to pump as they are manufactured by different sewage grinder pump manufacturers. When there is a malfunction on the sewage grinder pump, the sensor alerts the homeowner. The tank is often made of fiberglass-reinforced polyester, high-density polyethylene, or fiberglass and it has an inlet and exit opening. The pipes from the home connect to the entry opening while the pipe that connects the sewer line is connected to the discharge opening.

Figure 1: Installation of grinder sewage pump station.

Sewage grinder pump Types:

There are three types of sewage grinder pumps which are single-stage centrifugal sewage grinder pump, two-stage centrifugal sewage grinder pump, and semi-positive displacement sewage grinder pump.

Single-stage centrifugal sewage grinder pump

A single-stage centrifugal sewage grinder pump is a pump that employs a single impeller that spins on a shaft. This type of sewage grinder pump is powered by an electric motor that empowers it to pump the media needed. Wastewater components are pumped via the cutters that are responsible for cutting, grinding, or shredding the particles that might be in the sewage. The single-stage centrifugal sewage grinder pumps are used in areas that need lower discharge heights that are less than 90 feet.

Two-stage centrifugal sewage grinder pump

A two-stage centrifugal sewage grinder pump works the same way as a single-stage centrifugal sewage grinder pump but it employs two impellers. For the two-stage centrifugal sewage grinder pump, the working lift height is around 140 feet.

Semi-positive displacement sewage grinder pump

Semi-positive displacement sewage grinder pump is a sewage grinder pump that gets power from an electric motor and then turns a stainless steel rotor that rotates in a rubber stator to create pumping action. Semi-positive displacement sewage grinder pump enables pumping through higher heights by squeezing the media in a rubber stator thus pumping the wastewater into the basin. This type of sewage grinder pump is used where higher discharge heights are needed that is lift height of 140 feet or even higher.

Specifications of sewage grinder pump

The main specifications considered when selecting or buying a sewage grinder pump are pump head, flow rate, power rating, horsepower, pressure, operating temperature, and outlet diameter.

Sewage grinder pump materials

When selecting sewage grinder pumps it is also important to consider the material on the base of the pump. This is because the media being pumped could be acidic, abrasive, tacky, hazardous, caustic, very cold, or very hot. Sewage grinder pump manufacturers tend to use three common materials to make the base of the pump drum so as to have the advantage of handling media with different properties. These materials are plastic, stainless steel, and iron.

Stainless steel

Stainless steel is used in sewage grinder pumps to protect the pump against rust and chemical corrosion, as well as make it handle higher pressure compared to other materials like plastics.


Sewage grinder pump manufacturers tend to use plastics in making the base because it provides superb corrosion resistance as well as offers protection from a wide range of chemicals.

Cast iron

Cast iron material is used by sewage grinder pump manufacturers to make the pump more resistant to abrasion and forces due to the high pressure of the medium being pumped.

Advantages of sewage grinder pump

  • Sewage grinder pumps help to turn flushable into fact. The use of sewage grinder pumps helps to make sure the media being pumped is shredded into flushable pieces, unlike other sewage pumps that do not shred particles increasing the risk of making pipes to block.
  • Sewage grinder pumps enhance the use of a smaller footprint. Through sewage grinder pumps, the sewage components are rendered into a slurry that ensures smaller pipes can be used. With smaller pipes, it will reduce the space needed for the main sewer.
  • Sewage grinder pumps respect the environment. Sewage grinder pumps have high pumping power that helps them respect the terrain, unlike gravity sewer systems. Also, the sewage grinder pumps ensure there is a consistency to the sewage components they are transporting.
  • Sewage grinder pumps enhance flexibility. There are situations that at other times may need the use of a septic system. However, with sewage grinder pumps such situations are not a challenge. A single sewage grinder pump helps to hook up a household to the main sewer for a mile without problems.
  • Sewage grinder pumps do make alerts in case of malfunction. Sewage grinder pumps are manufactured with a sensor and alarm that are connected to the house it is serving. The alarm notifies the house owner of a problem before that problem reaches the building. This helps the owner that he/she needs to stop using the pump before it gets more damaged.

Disadvantages of sewage grinder pump

  • Sewage grinder pumps tend to become clogged because of the buildup of grease and dirt resulting in blockage.
  • When the sewage grinder pump becomes clogged once it can even ruin the starting components or electric motor.
  • Sewage grinder pumps tend to be expensive and require a control system that adds its cost.
  • Sewage grinder pumps consume a lot of energy because of the torque required to shred particles as well as the energy required to pump the sewage media.
  • Sewage grinder pumps last for a few years and then they need to be replaced or repaired even when they are in ideal conditions.

Sewage grinder pump application

Sewage grinder pumps are used to pump sewage. Wastewater from households collects in a tank and when it reaches a certain level the pump turns on to shred the waste and pump it through pipes onto the main sewer.

Sewage grinder pump troubleshooting

Clogging. Some materials such as paint, kitty litter, oil, and disposable napkins when poured or flushed down the drain are likely to build up and cause clogging in a sewage grinder pump. Clogs could result in more problems such as sewage leaking. When this problem occurs, the pump needs to be washed periodically using a garden hose.

Clotting. When the sewage grinder pump starts making a whirring noise when it is operated is commonly a sign of clotting. Clotting can make the sewage grinder pump operate more slowly. When this problem occurs the best solution is to contact a plumber to clean the pump.

Freezing. When a sewage grinder pump is installed in very cold regions and the sewage grinder pump is not buried deep below the frost line, the wastewater starts freezing and finally it damages the internal parts of the pump. The solution to this freezing problem is to place the sewage grinder pump deeper below the frost line.


This article has considered sewage grinder pump, working principle, its components, types, advantages, application, and troubleshooting. A sewage grinder pump is a pump that has a grinding mechanism to shred particles into a slurry that can be pumped in small-sized pipes and also ensure there is no blockage due to large-sized particles being transported. The sewage grinder pump should not be used to pump media that has high levels of sand as it can make it malfunction.

There are three types of sewage grinder pumps which are single-impeller centrifugal pump, double-impeller centrifugal pump, and semi-positive displacement pump. There are some factors to consider before purchasing a sewage grinder pump such as pressure, flow rate, head required among others. The sewage grinder pump base part drum can be made of different materials such as stainless steel, plastic, or cast iron. These pumps have advantages and disadvantages. However, the advantages outweigh the disadvantages by far.