All about pumps

By Rory Macnamara

Septic pumps, sewage pumps, and sewage ejector pumps are designed to remove sewage from a building where plumbing fixtures and their drains are lower than the building sewer line and/or septic tank.

Pumps used for drain and sewer cleaning Hawk PumpsTypical pumps used for drain and sewer cleaning.
Image credit: Hawk Pumps

Septic pumps must move solids, either by being able to pass large solid objects through the pump without clogging, or by grinding the solids into fine debris.

A sewage pump may be designed to pass solids up to a certain size, or it may be a sewage grinder pump designed to macerate solid waste so that it can be pumped through a sewer line — perhaps a smaller diameter ‘force main’ sewer line to a public sewer or septic tank.

Sewage grinder/ejector pumps are available in various horsepower models, typically from .5 to 1hp for residential applications, and are sold to operate at various voltages, including 110–120V, 220–240V, 440–480V, and even 600V models using either single-phase (most common) or three-phase motors.

Be sure to select the proper septic- or sump pump type.

Typically, the piping connection from the ejector pump to the building sewer line is 2" and incorporates a check valve.


Septic effluent pumps are used to move clarified septic effluent from a pumping chamber to a drain field.

Septic effluent pumps do not have to move solids, but are built to standards of durability and duty cycles more demanding than a typical sump pump used to remove ground water from a building.

Typical examples of applications where septic effluent pumps are used include raised bed, mound, or sand-bed filtration septic systems in which the absorption bed is located higher than the septic tank.

In these installations, septic effluent is pumped from a final chamber in the septic tank or from a second effluent chamber up to the absorption system.

Sewage Pump Xylem webAn example of a sewage pump.
Image credit:

Pump manufacturers may show that the same pump models can serve as a sump pump, effluent pump, and dewatering pump. But that is not universally the case: some sump pumps work just fine as effluent pumps, but other sump pump models (such as low-cost sump pumps using a vertical float and rod switch and intended for indoor dewatering in basements) may not be suitable for septic effluent pumping. It also may not be designed to be used in a septic effluent tank or drywell.

Be sure to select the proper septic- or sump pump type. The distinction among sewage pumps or septic pump types is important when installing or repairing a septic system that uses pumps, since choosing the wrong pump can mean a short operating life for the pump, an unreliable septic system, and unnecessary expenses.

Beware: there may be some confusion, depending on with whom you speak, because people do not always use the right terminology for construction or septic system parts. The correct sewage pump term — or the correct septic handling product versus the wrong one — can be an important distinction.

In a pinch, we have seen people use sump pumps for septic tank effluent pumping, but that is not a durable nor a recommended solution.


Velocity pumps

Rotodynamic pumps (or dynamic pumps) are a type of velocity pump in which kinetic energy is added to the fluid by increasing the flow velocity. This increase in energy is converted to a gain in potential energy (pressure) when the velocity is reduced prior to or as the flow exits the pump into the discharge pipe.

Submursible Waste PumpA submersible waste pump.
Image credit:

Positive displacement pumps

The positive displacement principle applies in these pumps:

  • Rotary lobe pump
  • Progressive cavity pump
  • Rotary gear pump
  • Piston pump
  • Diaphragm pump
  • Screw pump
  • Gear pump
  • Hydraulic pump.

Impulse pumps

A device for forcing running water to a higher level by using the kinetic energy of flow; the flow of water in the supply pipeline is periodically stopped so that a small portion of water is lifted by the velocity head of a larger portion. Also known as a hydraulic pump.

Gravity pumps

A pump deals more with differences in pressure than with gravity itself. At ground level, the pressure is said to be atmospheric pressure (about 10^5 pascals). A pump sucks some air from a pipe, with a piston reducing the pressure inside the pipe (less than the standard atmosphere).

Buoyancy pumps

The basic principle of buoyant energy (buoyant hydraulic energy storage system) is based on the well-established technology behind pumped hydro-energy storage plants. The major difference is the arrangement and location of reservoirs at such plants.


Here we use sewage pump and septic pump as synonyms. Both classes of pumps handle black water or sewage — it is the destination that differs.

A sewage pump, strictly speaking, is pumping black water (toilet waste) to a public sewer line.

Conversely, a septic pump, strictly speaking, is pumping black water (toilet waste) to a private septic tank and drain-field system.

But people use these terms loosely, and even among manufacturers it is important to ask for or to read the manufacturer’s description of what a particular pump model is intended to handle.

In addition, even among sewage pumps and grinder pumps that are intended to either pass solids or grind solids up and pump them, the vulnerability of different pump models to damage, clogging, or motor burn-up from debris that people may flush down drains and toilets varies.

Sump pumps are designed to remove unwanted water, such as surface or ground water that leaks into a building. Sump pumps only have to pump water, never solids.

A sump pump is normally installed in a pit at the low end of a basement or crawl space floor.

In a bad building water entry situation, water runs across the basement/crawl space floor into the sump pit from where it is pumped away (after already wetting the building and inviting a mould contamination problem). This condition pertains when water is entering a building through foundation walls, often because the roof drainage or surface run-off is directed right against the building foundation itself.

Sewage Pump Internal BreakdownThe internal breakdown of a sewage pump.
Image credit:

Keeping gutters and leaders working and correcting outside drainage errors are critical in keeping water out of a building. Does it not make more sense to prevent water from coming into a building than to let it in and then pump it out?

In a good situation, openings in the sides and bottom of the sump pit, or an underfloor drainage system, direct subsurface water into the sump pit before the ground water level rises enough to send water into the building.

Over several years of operation, and partly by pumping a little soil silt as it operates, a sump pump may actually improve the flow of underfloor water into the sump pit, thus reducing building water entry.


Sustainable development of the pump and related industries, including all participants, by:

  • Providing skills and training:
    • Provide training to new labour entrants into the industry;
    • Provide a platform where the ‘experienced’ can hand over their skills and knowledge to the ‘young’.
    • Providing networking opportunities:
  • Provide a platform for suppliers, manufacturers, end users, employers, and labour to meet informally and develop an understanding of each other’s challenges within the industry and create symbiotic relationships.
    • Encouraging transformation and local content through the creation of a peer-regulated certification process:
      • Encourage local content and transformation development without the sacrifice of sustainability.
  • Lobbying the relevant government departments to put in place the correct framework to provide the industry with the opportunity to further develop and expand.

Click below to read the July 2017 issue of Plumbing Africa

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