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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.
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 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.
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Questions & answers or comments about duplexing or doubling septic and sewage ejector pumps
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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.
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.)
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
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
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)
"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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