Plumbing drainage systems are designed and installed based on a simple principle: gravity causes water to flow downhill. The pipes from each plumbing fixture in a home that run to the municipal sewer line or backyard septic tank slope downward at an average of a quarter-inch of drop per foot of length of pipe, and that is normally sufficient to keep the drains free-flowing.

   But if the outlet of the plumbing fixture is below the inlet to the sewer or septic tank, or if it is higher but so far away that the necessary downhill slope cannot be accomplished, then a grinder pump is added to the system to push the effluent through the pipe. Typical situations in our North Florida area where a grinder pump is necessary would be where the home is sited on the side of a hill and lower than the sewer line at the street, or when an addition to an existing house puts the new plumbing fixtures too far away from the septic tank to get adequate downhill slope of the pipe along the run. In northern climates, they are also often required for basement plumbing fixtures.

   The device itself is usually concealed underground, and its presence is identified by an alarm box with flashing light on top and loud horn that goes off when the tank reaches an overflow level due to a malfunction.  The photo above shows a typical grinder pump in a backyard for a septic tank, and the photo below is a wall-mounted alarm box that you might see in the garage or on the exterior wall of a home.

   The grinder creates a slurry out of the household waste, which makes it easier to pump, then it is collected in a small holding tank until a sufficient amount has accumulated and the pump cycles on to empty the tank.

   Grinder pumps are not designed to handle diapers, feminine hygiene products, aquarium gravel, seafood shells, grease or caustic chemicals. So don’t flush anything that cannot be readily ground up or will damage the equipment.

   If the grinder pump has been installed by the local city or county sewer authority, you may not be responsible for its maintenance or replacement. Otherwise, an occasional service call from a plumber may be necessary when the system stops pumping and the alert system sounds off.

    Also, see our blog posts Should I call a plumber or septic tank contractor when my septic tank backs up into the house? and Do I have to get a larger septic tank when I build a home addition?

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  To learn more about SEPTIC TANK SYSTEMS, see these other blog posts:

• What are the building code requirements for gray water reuse in Florida?

• What can I add to my septic tank to help it work better? 

• Why do septic tank contractors want you to get rid of your kitchen disposal?

• How can I tell if a house is connected to a septic tank system or sewer?

• How can I locate my septic tank?

• Does a septic tank have to be re-certified if a house has been vacant for a while? 

• How often should I pump out the septic tank?

• Where is the septic tank? Are you going to inspect it? • Can a house have more than one septic tank?

• What is the difference between gray water and black water in the plumbing code? 

• Is it alright to disconnect the washing machine drain from the septic tank and divert it to the ground in the yard?

    Visit our PLUMBING and SEPTIC TANK SYSTEMS pages for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.