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Installation Guide for Duplex Septic Pump & Sewage Pumping Installations
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InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.
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.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
Duplex Septic Pump System Designs
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. This duplex septic pump article is part of our series: Inspecting, Testing, & Maintaining Residential Septic Systems an online book on septic systems
.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.
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:
- 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.
- 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 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
Frequently Asked Questions (FAQs)
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
- 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
- Septic Tank/Soil-Absorption Systems: How to Operate & Maintain [ copy on file as /septic/Septic_Operation_USDA.pdf ] - , Equipment Tips, U.S. Department of Agriculture, 8271 1302, 7100 Engineering, 2300 Recreation, September 1982, web search 08/28/2010, original source: http://www.fs.fed.us/t-d/pubs/pdfimage/82711302.pdf.
- 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.
- Ten Steps to Keeping a Septic System Working, suggestions from the U.S. EPA, edits and additions by DJF
- 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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Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.
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- Inspecting Septic Systems: Online Book, Inspection, Test, Diagnosis, Repair, & Maintenance: our Online Septic Book: Septic Testing, Loading & Dye Tests, Septic Tank Pumping, Clearances, details of onsite waste disposal system inspection, testing, repair procedures.
- Advanced Onsite Wastewater Systems Technologies, Anish R. Jantrania, Mark A. Gross. Anish Jantrania, Ph.D., P.E., M.B.A., is a Consulting Engineer, in Mechanicsville VA, 804-550-0389 (2006). Outstanding technical reference especially on alternative septic system design alternatives. Written for designers and engineers, this book is not at all easy going for homeowners but is a text I recommend for professionals--DF.
- Builder's Guide to Wells and Septic Systems, Woodson, R. Dodge: $ 24.95; MCGRAW HILL B; TP;
Quoting from Amazon's description: For the homebuilder, one mistake in estimating or installing wells and septic systems can cost thousands of dollars. This comprehensive guide filled with case studies can prevent that. Master plumber R. Dodge Woodson packs this reader-friendly guide with guidance and information, including details on new techniques and materials that can economize and expedite jobs and advice on how to avoid mistakes in both estimating and construction. Chapters cover virtually every aspect of wells and septic systems, including on-site evaluations; site limitations; bidding; soil studies, septic designs, and code-related issues; drilled and dug wells, gravel and pipe, chamber-type, and gravity septic systems; pump stations; common problems with well installation; and remedies for poor septic situations. Woodson also discusses ways to increase profits by avoiding cost overruns.
- Country Plumbing: Living with a Septic System, Hartigan, Gerry: $ 9.95; ALAN C HOOD & TP;
Quoting an Amazon reviewer's comment, with which we agree--DF:This book is informative as far as it goes and might be most useful for someone with an older system. But it was written in the early 1980s. A lot has changed since then. In particular, the book doesn't cover any of the newer systems that are used more and more nowadays in some parts of the country -- sand mounds, aeration systems, lagoons, etc.
Design Manuals for Septic Systems
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US EPA Onsite Wastewater Treatment Systems Manual [online copy, free] Top Reference: US EPA's Design Manual for Onsite Wastewater Treatment and Disposal, 1980, available from the US EPA, the US GPO Superintendent of Documents (Pueblo CO), and from the National Small Flows Clearinghouse. Original source http://www.epa.gov/ORD/NRMRL/Pubs/625R00008/625R00008.htm Onsite wastewater treatment and disposal systems,
Richard J Otis, published by the US EPA. Although it's more than 20 years old, this book remains a useful reference for septic system designers.
U.S. Environmental Protection Agency, Office of Water Program Operations; Office of Research and Development, Municipal Environmental Research Laboratory; (1980)
- Eco John® Innovative Toilet Solutions, Global Inventive Industries, Fountain Valley CA, PDF, product brochure
- "International Private Sewage Disposal Code," 1995, BOCA-708-799-2300, ICBO-310-699-0541, SBCCI 205-591-1853, available from those code associations.
- "Manual of Policy, Procedures, and Guidelines for Onsite Sewage Systems," Ontario Reg. 374/81, Part VII of the Environmental
Protection Act (Canada), ISBN 0-7743-7303-2, Ministry of the Environment,135 St. Clair Ave. West, Toronto Ontario M4V 1P5 Canada $24. CDN.
- Manual of Septic Tank Practice, US Public Health Service's 1959.
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