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Duplex septic pump installationDuplex Septic, & Sewage Pump Installations

Types, features, instructions

Duplex septic pumps or sump pumps:

For critical systems such as a sewage system that depends on pumps for operation or a building that depends on sump pumps to keep water out of a low area, duplexing the pumps along with appropriate controls and periodic testing is an important step.

This article describes the reasons & methods for installing duplex versions of septic pumps, septic sump pumps, sewage ejector Pumps, septic grinder pumps, & pumps in sewage pumping stations.

Advice is given for septic tank effluent or sewage pump selection and use.

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Duplex Sump & Septic Pump System Designs

Battery backup dual sump pump installation, adapted from Glentronics cited & discusse at InspectApedia.com To avoid confusion note that duplex and backup pump systems may be used for either

Shown here, our illustration, adapted from Glentronics sump pump instructions cited below, describes details of a typical battery-backup dual-sump pump installation.

[Click to enlarge any image]

Septic pumps used for pumping air in aeration systems and septic pumps used to move effluent in a drip dispersion system are discussed under the appropriate septic system type which are outlined

at SEPTIC SYSTEM DESIGN ALTERNATIVES.

There are two common pump-pair or duplex sump or septic grinder pump system setups. Either of these is found at municipal lift stations and similar installations and also in buildings where a backup or extra capacity is needed for water removal.

1. Alternating septic pumps:

 two septic pumps alternate, taking turns running - I prefer this method as you are spreading the wear over two pumps and you'll know when one fails and have a chance to repair it.

The two sewage grinder pumps are installed at the same location but are wired so that the pumps take turns, first one, and next cycle the other pump is turned on by the float switch.

However this system lacks the ability to handle surges in wastewater load unless additional controls and wiring are installed to make the pump also come on in response to high waste levels such as in the reserve septic backup design discussed next.

2. Reserve septic backup design:

 the backup septic pump never runs unless the primary septic pump has failed or is overloaded.

A simple installation provides a pump control float switch that turns on the backup pump only when effluent or sewage in the pumping chamber reaches a level above that normally handled by the primary septic pump.

This approach provides both pump backup and the ability to handle surges in sewage loads on the system.

Handling surge loads on the septic system: 

A duplex septic pump system in which the second pump can come on as effluent level rises in the pumping chamber handles either unusual flows into the system (uncommon) or the case where the 1st pump is broken. I don't like this setup as much as we're never testing pump #2 until the very day it's absolutely needed.

Septic Pump controls for two-pump duplexed septic systems 

are produced by several manufacturers including Anchor Scientific, Aquawarx (control panels), B/W Controls, Orenco, Rhombus, SJ Electro, and CSI.

Reliability requirements define when a duplex sewage grinder pump or septic pump system is appropriate

Wile single grinder pump systems are often installed to support an extra basement bathroom, where a sewage pump is handling an entire home or larger facility, duplex septic pumping systems (shown in the photo at the top of this page) are preferable for their greater reliability. There are two principal advantages of a two-pump septic system:

  1. Septic system reliability:

    If either sewage pump fails the second unit can keep the building's plumbing system operating while the failed pump is repaired.

  2. Handling surge loads in a septic system: 

    If the building is one which experiences surges in wastewater loading, the duplex sewage pump design option #2 described below can handle this extra wastewater load without a system backup.

(Remember that in a power outage your pump system will not work unless you've provided backup power.)

Inspecting Duplex Septic Pump Systems

Additional details about the installation of sewage grinder or septic pumps and how to inspect them can be found at SEWAGE EJECTOR / GRINDER PUMPS

Beyond those suggestions, when inspecting a duplex septic pump system, remember to assure that both pumps are in working condition and that the switch between them is functioning. Simply turn off power to one pump to confirm that the second one will operate, and vice versa.

Duplex Septic Pump or Sump Pump System Alarms

Duplex septic pump alarm installation

A duplex septic pump system is installed where septic and plumbing system reliability are very important. That same requirement makes it important for the building occupants or maintenance staff to know if one of the pumps has failed, so that a repair can be ordered before both pumps stop working.

A duplex septic pump alarm system accomplishes this function and can also diagnose the system by indicating which pump has stopped operating.

Here is a photo of a typical alarm system for a duplex sewage grinder pump installation.

We discuss septic system alarms in more detail at SEPTIC PUMP ALARM SYSTEMS

This duplex septic pump article is part of our series: SEPTIC SYSTEM INSPECTION & MAINTENANCE COURSE an online book on septic systems

Also see FLOOD ALARMS


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