Grinder Pump FAQs

What is a grinder pump?

A grinder pump works like a household garbage disposal, but on a larger scale. It grinds up wastewater produced in your home (i.e. toilet use, shower, washing machine, etc.) and pumps it into the public sewer system.

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How does it work?

A grinder pump is placed in a tank (or well) that is buried in a convenient outdoor location on a homeowner’s property (grinder pump units also can be purchased for inside installation). The tank provides wastewater holding storage capacity. When water is used in the house, wastewater flows into the tank. When the wastewater in the tank reaches a pre-set level, the grinder pump automatically turns on, grinds the waste, and pumps it out of the tank via the homeowner’s on-site sewer service line and into the public sewer system. A grinder pump will normally run for one or two minutes and automatically turn off when the tank is emptied. The pump is powered by electricity and is connected to a control panel near your electric meter.

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Why do some homes/businesses need grinder pumps?

Grinder Pump Diagram

In most instances, wastewater flows by gravity from a home/business’ on-property sewer service line to a public sewer main where it travels to wastewater treatment plants. At the plants, the wastewater is cleaned, disinfected and safely returned to the environment. However, because of elevation, gravity may not work in all instances. In situations where a home/business’ sewer service line leaves the building at a lower elevation than the public sewer main, a grinder pump is sometimes used to grind and pump wastewater to the main. See diagram below illustrating typical grinder pump layout.

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Who is responsible for the grinder pump?

Most of the 1,500 grinder pumps in Montgomery and Prince George’s Counties are on private property and therefore are the responsibility of the property owner. The same is true for the private sewer service line on the home or business owner’s property. WSSC Water’s responsibility for sewer service begins after the property line in the public right-of-way.

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What can I do to protect my grinder pump?

A properly maintained grinder pump should be able to handle wastewater from the kitchen, bathroom, laundry, etc. However, some chemicals and substances can adversely impact a grinder pump and may cause safety hazards. Please check the labels on all chemicals before using / disposing. Also, never pour the following items down drains or flush down toilets:

  • Grease (a byproduct of cooking that comes from meat fats, oils, shortening, butter, margarine, food scraps, sauces and dairy products);
  • Explosive or flammable material;
  • Kitty Litter;
  • Aquarium gravel;
  • Strong Chemicals or toxic, caustic or poisonous substances;
  • Degreasing solvents;
  • Diapers, feminine products, or cloth of any kind;
  • Fuel or lubricating oil, paint thinner of antifreeze;
  • Plastic objects; and
  • Seafood Shells.

These items can damage the grinder pump and its controls, cause blockages and backups and may create unsafe conditions in your lines and tank. Also, never connect a sump pump to sewer lines. Doing so is a violation of the WSSC Water Plumbing and Fuel Gas Code and decreases the sewer mains’ flow capacity while increasing wastewater treatment costs. In the case of a grinder pump, a sump pump connected to the sewer system may raise your electric rates and shorten the life of your grinder pump. 

The homeowner shall be responsible to maintain the ground around the pump basin within a 5 foot radius so that the ground is sloped enough to prevent rainfall from pooling next to the basin and entering the lid or vent.  Grinder pump tanks have an air vent located on the side of the tank, just below the cover. This vent must be kept open and free of debris, such as mulch or grass, for the unit to remain operational.  Grinder pumping systems are designed to handle wastewater that is normally discharged to the sewer from the kitchen, bathrooms and laundry. However, rain water draining into the grinder pump basin may overload the system and cause slower pumping rates which may potentially create sewage back-ups.  Additionally, the WSSC Water Plumbing and Gas Code (latest edition) prohibits the connection of sump pumps to the public sewer system.  Inflow from sump pumps, downspouts, and foundation drains are disallowed and may also overload grinder pumping systems.


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How do I properly maintain my grinder pump?

In addition to following the tips provided in question #5, please follow the manufacturer’s recommended maintenance guidelines.

In the event you have misplaced these guidelines, only two types of grinder pumps are currently approved for use in the WSSC Water service area:

F.E. Myers and Environment One. Please contact either company for manufacturing details at (888) 987-8677 for Myers and (518) 346-6161 for Environment One.

** Remember that your grinder pump is powered by electricity. In the event of a power outage, your pump will not work unless it is powered by a generator.

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What should I do with my pump when I go on vacation?

If you plan on being away for several days, replace the wastewater in the tank with clean water to help minimize odors.

To do this,

  1. run an inside faucet for about 10 minutes – long enough for the grinder pump to start working (you may need to go outside near the pump and listen to verify it has started).
  2. After the pump starts, turn the inside faucet off.
  3. The pump will run until the tank is empty and shut off automatically.

This process will cleanse the pump and keep it filled with a minimum amount of clean water. Remember to always leave the power to the pump on.

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