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Guide to Single vs Duplex Sump Pump Installations SepticAPedia ©

• When should we install more than one sump pump; how to wire duplex sump pump installations.
• Where and how to install sump pumps
• How to inspect & maintain sump pumps to remove water from buildings or to prevent basement leakage or crawl space water entry

This article explains when, where, and how multiple or duplex sump pumps are used in buildings, describes the types of sump pumps, and describes how sump pumps should be installed, inspected, and maintained.. 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."

© 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.

Two Types of Sump Pump Installations - Simplex and Duplex Pumps

A sump pump is normally installed in a pit at the low end of a basement or crawl space floor or in another location where water needs to be removed such as in a boiler pit or an outdoor well pit. On occasion we find that we need to install two or more sump pumps inside or outside of a building foundation to remove water from around the foundation of a poorly-sited (too low) building which has no natural drainage path to dispose of ground water by gravity.

Single submersible or pedestal sump pump: The photo on the left is what you're likely to see if your basement has a modern sump pump.

A pedestal type pump must keep its motor out of water and dry.

Regardless of which type of pump we select, pedestal or submersible sump pump, many installations require that only one single pump be installed.

We discuss the details of submersible and pedestal sump pump types at Four Common Types of Sump Pumps.

Duplex sump pumps: The photo at left shows a duplexed sump pump system using pedestal type sump pumps. This was a really wet basement - a single sump pump simply could not keep up. In this installation .

When a building footprint or foundation layout is complex, or where the building is constructed over both basement space and one or more crawl spaces, it may be necessary to install multiple sump pumps to protect these various areas.

In a single large basement whose floor did not slope uniformly to a single low corner, it may be more economical to install two or even more sump pumps in problem areas than to tear up the entire basement floor to install a sub-slab drainage system.

Two Types of Duplex Sump Pump Installations: Alternating and Reserve

Reserve septic backup design: the backup pump never runs unless the primary pump has failed or is overloaded. A simple installation provides a pump control float switch that turns on the backup pump only water in the pumping chamber reaches a level above that normally handled by the primary sump pump. This approach provides both pump backup and the ability to handle surges in building water entry loads on the sump pump system.

Alternating septic pump design: the two sump 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.

This dual pump hookup is more common among septic pumping stations than among home sump pump de-watering systems, but it may be appropriate where a large volume of ground water has to be kept constantly out of a building. An example we've seen was in the basement of a home on Long Island, NY in which the level of the basement slab was so low that flooding from Long Island sound would be nearly constant if the pumps failed.

The alternating sump pump approach has the advantage that both pumps are being exercised regularly, which reduces the chance of the ugly discovery that in the event you have to rely on a backup sump pump which has been sitting idle, waiting its chance to run, has in the interim, died.

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SUMP PUMPS
    Sump Pump Types
    Sump Pump Single vs Duplex
    Sump Pump Discharge
    Sump Pump Inspection

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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