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How Do Septic Lift Stations Work?

Chris Deziel
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When a septic tank must be located below the drainfield, a lift station transfers water from the tank to the field.

If your house is in a rural location, you may be "off the grid" as far as your plumbing system is concerned; that usually means you get your water from a well and that a septic system serves your waste management needs. The two main components of a typical septic system are the storage tank and the drainfield, and if the slope of the land allows, gravity transfers water between them. If topography requires the tank to be located below the drain field, however, the system needs a lift station. Because it's crucial to the operation of the system, it's good to understand how your lift station works.

Lift Station Components

Transfer Pump

The heart of the lift station, a submersible pump inside the tank pumps water out of the tank whenever the water level rises to a predetermined point. Inside the pump, a rotating impeller moves water through a watertight system of pipes to the distribution box. The pump must be sized according to the vertical pumping distance and the size of the pipes. Ancillary components include:

  • Casing -- The pump is often inside a casing to prevent solid matter from flowing into it. In some septic tanks with effective baffle systems, the casing may not be required. 
  • Cover -- A manhole cover directly over the pump provides access to it. 
  • Float -- The pump comes on when the water level activates a float that triggers it. The float may be pressure-activated, or it may be mechanical, much as the float inside a toilet tank. 
  • Alarm -- If the level rises to a preset level above that which activates the float, it triggers a second float, which sounds an alarm to alert the building occupants that the pump isn't working. 

Distribution Box

The distribution box -- or D-box -- is located at the highest point on the drain field. It has an inlet pipe from the tank and an outlet pipe to each branch of the drain field. It's typically a rectangular concrete box with a concrete cover and, like the septic tank, it's usually buried.


The piping that connects the septic tank to the distribution box is usually 3- or 4-inch PVC, but on some older systems, it may be made of cast iron or clay. This pipe is also buried, and like the plumbing pipes in your house, it can clog. Tree roots and improper tank maintenance are common reasons for clogs.

The main components of a lift station are a transfer pump, a distribution box and pipes to connect them. A number of ancillary components are needed to ensure the pump operates properly and in a timely way.

Lift Station Maintenance

Proper septic maintenance is even more important when a lift station is involved; the pump is breakable, and if it goes out of commission, the system cannot be used until it's repaired.

  • Inspect your tank yearly and pump the tank when the sludge occupies more than 1/3 the volume of the tank. 
  • Avoid flushing anything that won't decompose, including diapers, tampons and excessive amounts of paper. Solid objects in the tank can find their way into the pump and clog or break it.
  • Check the D-box periodically. If all is well, the box should contain only water -- the presence of sludge and solid matter is a sign the tank needs pumping. 
  • Test the alarm periodically by pressing the test button -- if there is one. The alarm is a safeguard against a potentially disastrous tank overflow in the event of pump failure, so you want to make sure it's working properly. If your alarm doesn't have a test button, consider installing one.