Grinder Pumps

by Nick Gromicko, CMI®

Grinder pumps are waste-management devices used to grind up household waste into a finely ground slurry and then force it into the sewer system. Grinder pump installation

Grinder pumps are required where a building’s drain system is at a level below a municipal sewer line or septic tank. Even if a building is at the same level as its sewer line or septic tank, the geography of the site may prevent sewage from flowing fast enough by gravity alone, making a grinder pump necessary. A typical application of a grinder pump is in a home where a basement bathroom is located lower than the height of the sewer line that leaves the home.

How do they work?

Household wastewater flows into the grinder pump’s tank. When the wastewater reaches a pre-set level, the grinder automatically turns on, grinds the waste, and pumps it into the public sewer system or septic tank. Grinder pumps will normally run for a few minutes and turn off when the tank is emptied. The pump is powered electrically and is connected to a control panel near the electric meter.

Maintenance, Inspection and Repair 
Inspectors can pass the following tips on to their clients:
  • If installed in the yard, the pump must be buried deep enough that it is below the frost line. Frost lines vary based on geography.
  • Grinder pumps should never be connected to sump pumps, as this connection may raise electricity rates and shorten the life of the grinder pump.
  • Never plant shrubs or flowers, construct fences, decorative pilings, or dig ponds above the pump.
  • While on vacation, there are certain things homeowners must do to minimize any stagnating odors:

    • Run water long enough for the grinder pump to activate. This will cleanse the pump and leave the tank with only clean water.
    • Leave the electricity on. The pump’s heating element needs to be on to eliminate condensation and freezing.
  • Do not dig between the control panel and the tank because digging may damage electrical power and alarm wires.
  • Limit water use during a power failure. Although the tank has a holding capacity that may accept wastewater during a power failure (depending on how much waste was in the tank before the power outage), the pump will not be able to operate without electricity.
  • Some older grinder models have a small breather vent located just below the cover on the side of the tank. This vent must remain open and free from debris, such as grass and leaves, for the unit to operate properly. These older models should also have the ground sloped away from the tank vent so water will not collect and enter the vent, which may break the unit.
  • Instruct your clients to never pour the following items down drains or flush down toilets, as they may damage the grinder pump and its controls, cause blockages and backups, and create unsafe conditions in the lines and tank:
    • aquarium gravel;
    • degreasing solvents;
    • diapers, feminine hygiene products, or cloth of any kind;
    • explosive or flammable material, such as gasoline or lighter fluid;
    • kitty litter;
    • grease. Grease buildup may cause the pump to turn on unnecessarily or cause the pump to not turn on at all. In the latter case, the tank may fill up, causing sewage to back up into the home or yard;
    • plastic of any kind;
    • seafood shells; or
    • toxic or caustic chemicals.

      Note that these items should not be flushed in any home, regardless of whether it has a grinder pump, since such discarded matter may damage septic tanks and sewer systems.

For additional maintenance instructions, clients should follow the guidelines set by the manufacturer.

Homeowners may not be responsible for repairs to their grinder pumps; if the county owns the unit servicing the home, government technicians can provide maintenance and service at no cost. Privately owned systems may be covered under a warranty by the builder in houses that are less than a year old. For privately owned systems that are not under warranty, homeowners must contact a qualified plumber.