FEATURES
51
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.
Types of pumps
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.
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.
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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.
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.
The internal
breakdown of a
sewage 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).
July 2017 Volume 23 I Number 5