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Installation Guide for Duplex Septic Pump Installations InspectAPedia®  -

• Duplex septic pump system suggestions
• Septic tank pumps, septic grinder pumps, septic effluent pumps
• Sewage ejector pumps
• Sump Pumps
• Sewage Pumping Stations
• Septic Pump Alarm
• Septic Alarm demo video

This article describes the reasons for installing duplex versions of 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. 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. Citation of this article by reference to this website and brief quotation for the sole purpose of review are permitted. Use of this information at other websites, in books or pamphlets for sale is reserved to the author. Technical review by industry experts has been performed and is ongoing - reviewers welcomed and are listed at "References."

This document is a chapter of Inspecting, Testing, & Maintaining Residential Septic Systems an online book on septic systems.

© Copyright 2009 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

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.)

Duplex Septic Pump System Designs

There are two common pump-pair or duplex septic grinder pump system setups. Either of these is found at municipal lift stations and similar installations.

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. Tithe 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.

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 Pump Grinder Pump . 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 System Alarms

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

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SEPTIC SYSTEM PUMPS
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    What is a Sewage Ejector?
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More Information on Building Diagnostic Inspections and Repairs

• The Septic System Information Website home page for this topic
• Septic Systems Inspection, Testing, & Maintenance- online textbook. Detailed how to inspect, maintain, repair information
• The Home Buyer's Guide to Septic Systems
• Septic Tank Pumping Guide: When, Why, How to pump the septic tank
• Home & Outdoor Living Water Requirements
• Septic Tank Capacity vs Usage in Daily Gallons of Wastewater Flow, calculating required septic tank size, calculating septic tank volume from size measurements
• How Big Should the Leach Field Be? - table of soil percolation rate vs. field size
• Septic System Drainfield Absorption System Biomat Formation - what leads to drain field clogging and expensive drainfield repairs
• Table of Required Septic & Well Clearances: Distances Between Septic System & Wells, Streams, Trees, etc.
Pennsylvania State Fact Sheets relating to domestic wastewater treatment systems include

• Pennsylvania State Wastewater Treatment Fact Sheet SW-161, Septic System Failure: Diagnosis and Treatment
• Pennsylvania State Wastewater Treatment Fact Sheet SW-162, The Soil Media and the Percolation Test
• Pennsylvania State Wastewater Treatment Fact Sheet SW-l64, Mound Systems for Wastewater Treatment
• Pennsylvania State Wastewater Treatment Fact Sheet SW-165, Septic Tank-Soil Absorption Systems
• Document Sources used for this web page include but are not limited to: Agricultural Fact Sheet #SW-161 "Septic Tank Pumping," by Paul D. Robillard and Kelli S. Martin. Penn State College of Agriculture - Cooperative Extension, edited and annotated by Dan Friedman (Thanks: to Bob Mackey for proofreading the original source material.)

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