Buying, Installation & Maintenance Guide for Sump Pumps InspectAPedia® -
What is a sump pump? How do sump pumps remove building water or prevent water entry?
What types of sump pump can I buy?
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
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This article explains how 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."
Readers have asked the difference between a sump pump, simplex and duplex sump pumps, a septic effluent pump, a sewage grinder pump, and an effluent pump. Here we discuss the various types of pumps and their purchase, installation, inspection, and maintenance.
What is a Sump Pump?
Sump pumps, which we discuss on this page, are designed to remove unwanted water, such as surface or ground water that leak into a building. Sump pumps only have to pump water, never solids. Sump pumps are normally used to pump clear liquid, such as ground water from a wet basement sump pit or graywater from a
basement laundry sink. These pumps are light-duty and have no ability to pass solid debris other than perhaps fine soil or
silt that may be in groundwater. Some manufacturers may also call sump pumps de-watering pumps or submersible sump 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 sump pumps installed 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.
In a bad building water entry situation water runs across the basement/crawl space floor into the sump pit where it is pumped away (after already wetting the building and inviting a mold contamination problem). This condition pertains when water is entering a building through foundation walls, often because the roof drainage or surface runoff are directed right against the building foundation itself. Keeping gutters and leaders working and correcting outside drainage errors are critical in keeping water out of a building. Doesn't it make more sense to prevent water from coming into a building than to let it in and then pump it out?
In a good situation, openings in the sides and bottom of the sump pit, or an under-floor drainage system direct subsurface water into the sump pit before the ground water level rises enough to send water into the building. Over several years of operation, and partly by pumping a little soil silt as it operates, a sump pump may actually improve the flow of under-floor water into the sump pit, thus reducing building water entry.
Septic pumps, sewage pumps, grinder pumps, and effluent pumps are not sump pumps, and they are discussed beginning at Sewage Ejector Pump Grinder Pump.
The distinction among these pump types
is important. Choosing the wrong pump can mean a short operating
life for the pump, an unreliable system, and unnecessary expense. There may be some confusion, depending on with whom you speak, because people don't always use
just the right terms for construction or septic system parts - and the right sewage pump term, or right septic handling product versus
the wrong one can be an important distinction.
Two Types of Sump Pump Installations - Simplex and Duplex Pumps
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, many installations require that only one single pump be installed.
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 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.
Four Common Types of Sump Pumps
Submersible sump pumps, such as shown in the photo at left, use a motor housed in a water proof enclosure and a separate float that turns the pump on and off.
The sump pump float contains a position-activated switch and is connected to the submersible pump by a flexible wire. Some submersible sump pumps, such as the one shown here at left, use other types of float switches.
The submersible sump pump motor is capable of working when entirely under water.
A submersible sump pump uses a float switch intended to turn the pump on when
ground water rises in the sump pit (or flows stupidly across your basement and into the pit) where it is discharged to a storm drain or the property surface.
Watch out for debris or wiring in the sump pit that block movement of the float switch - your sump may fail to turn on.
Pedestal sump pumps, such as shown in the photo at left, use a motor atop a pipe inside which the pump turns a shaft which operates the pump impeller.
The pump impeller is located in a bottom pedestal which is under-water. You'll notice that the electric motor that powers the pump impeller is mounted on top a tall shaft that extends well out of the water itself.The float that turns the pump on and off usually looks suspiciously a lot like a toilet tank float, connected to a vertical rod.
Pedestal sump pumps are an older non-submersible type of pump used for removing water from buildings.
As rising water in the sump pit lifts the float, the float lifts the rod and the rod includes an adjustable screw-clamp fitting which pushes on the electrical contact of a mechanical switch to turn the pump on. As the water level drops the float falls and another screw-clamp fitting above the switch turns the pump motor back off.
Battery-backup sump pumps, use a rechargeable battery which is normally connected to live electrical power in order to remain fully charged. If electrical power fails, the batter can still operate the sump pump. We recommend this type of sump pump at homes where electrical power is frequently lost. You're most likely to lose electrical power during a storm, which may be exactly when you most-need the sump pump.
Water powered sump pumps, (as shown in the photos above) use municipal water pressure and a venturi fitting to pick up and eject water from a building during flooding. Usually they are turned on manually by opening a water valve near the pump. Water driven sump pumps work only where municipal water is provided.
Water powered sump pumps offer the advantage that the pump can operate when there is no electrical power. At least the older versions of these devices are illegal in many municipalities because their installation constitutes a cross-connection which can back-contaminate public water mains with unsanitary floodwaters. There may be newer versions that are code-approved: we invite more data and comment on this product. See CROSS CONNECTIONS, PLUMBING for more details about plumbing cross connections and sump pumps.
Water & flooding alarm products are available in a variety of forms including battery-powered devices (we show one at Sewage Ejector Pump Grinder Pump) and even devices which can turn a light in a home or make a telephone call or inform an alarm company if a building is being subjected to flooding. Considering the very high cost of flood damage cleanup and mold remediation, we consider flood alarms a great idea for buildings which are often left unattended.
Where does the sump pump send its Discharge Water?
In this photo at left a temporary sump pump discharge line has been left on the basement floor - no good destination has been assigned to sump outlet hose. If this sump pump is called-on to operate in this condition the building will simply be flooded.
Sump pumps that have been added to an older structure often pump their discharge to the ground surface where it runs to a storm drain or area drainage setting.
If you have such a system be sure that the sump pump discharge empties where it meets these criteria:
The water leaving the sump pump should be discharged to a location where it does not flow back towards the building. Otherwise it may simply cycle the same water endlessly, possibly even undermining the building foundation
Water discharge from a sump pump must go to a legal destination. In the photo at left we're emptying the sump pump via a small diameter (Limited flow capacity) to a local storm drain.
This might be legal and fine in the summer for an unusual event, but this is not a reliable, permanent sump pump installation.
As this system was found in Maine, we can expect it to freeze or simply not work in winter or early spring when it may be most needed.
Discharging onto a neighbor, and in some communities, discharging into local storm drains, may be prohibited and are certainly a bad practice.
In freezing climates, the sump discharge needs to be protected from freezing or the system may not work when most needed.
Guide to Inspecting Sump Pumps
Sump pumps on newly constructed buildings are often connected to the building foundation drain. We consider this a bad practice. It is a rare home more than 20 years old whose footing drains are intact.
If a footing drain discharge itself becomes clogged or damaged, sending the sump pump discharge into that system will not work: you'll simply flood another section of the building foundation, basement, or crawl space, or you may overload the existing foundation drain causing building water entry.
Connecting a sump pump to a municipal sewer drain is bad practice and illegal in some communities. You're adding to the municipal sewer plant's water overload during wet weather and you may thus be contributing to the discharge of raw sewage from the overloaded municipal treatment facility right into the environment.
Where permitted, we prefer to route a sump pump to a storm drain, or where soil conditions permit it might be discharged to a drywell.
Sump pump inspection list
Alarms for basement water: Water or Sump Pump Alarm protection: where a sump pump is relied-upon to keep water out of a building, good practice includes an alarm to inform someone when the pump is not operating. Various systems use a detector which senses water on a building floor near the sump pump. Water alarms can sound an alarm to building occupants, turn on a light in a window for a neighbor to see, notify a security service, or even place a telephone call to report this condition. We recommend this protection for any building which is left unattended for long periods.
Battery backup sump pump systems: in areas prone to power failures the sump pump may be a battery-backup installation. The batteries are connected to a charging system and are available to operate the pump when area electrical power has been lost. Turn off the electrical power to the charger and confirm that the pump is running on battery power. Review the specifications for the system to determine whether or not the pump may be able to continue to operate on battery power for the typical length of time that electrical power is lost.
Check valve: is a check valve installed on the sump pump discharge line? If not water will run back into the sump pit each time the pump shuts off. This defect causes extra cycles of pump operation and may reduce pump or switch life; in odd circumstances such as a sump pump discharge line into a stream, it can even back-siphon outdoor water into the sump pit and into the building.
Discharge line security: sump pumps cause a sudden surge in water through the discharge pipe when the pump comes on. Many sump pump installations use a flexible discharge pipe which is not adequately secured. As a result, each time the pump cycles on and off the flexible discharge pipe jerks and moves across various contact surfaces. We've seen this result in holes worn into the discharge pipe so that each time the sump pump cycled on it sprayed water across the basement.
GFCI protection: Is the sump pump connected to a GFCI-protected electrical circuit or outlet? According to some writers a sump pump should be connected to a GFCI circuit. But we find that wet locations sometimes keep tripping off the GFCI - a safe condition, but it means the building is likely to become flooded because the circuit powering it has shut down. Some writers and electrical inspectors make an exception to the more general GFCI-requirement rules for sump pumps.
Mechanical security: If a pedestal sump pump is installed, is it secured against tipping over? A tipped pump will jam its float and stop working.
Motor switch & Electric Motor: Does the pump's electric motor turn on in response to the float?
Pump impeller assembly: does the pump actually move water when the motor runs? Impellers can and should be cleaned of dirt, pebbles, and mineral deposits to keep the pump operating efficiently.
Sump Pump pit openings: Is the sump well or bucket properly opened to permit ground water to enter the pit directly? Our first home had a basement sump pump installed in a water tight steel bucket the builder had pushed through the basement floor. Water had to rise under the basement floor, leak into the basement, run across the floor, and then be pumped away. Making holes in that bucket allowed the pump to draw water from below the basement slab. It lowered the water table and stopped water from entering the basement through the foundation walls.
Sump pump water destination: is the pump delivering water to a legal destination and one which will not send water flowing back towards the building? Water should be discharged no less than 20 ft. from the building and to a spot which drains away from the building.
Trip hazards: Is the sump pit protected against someone tripping or falling into it?
If radon is a problem in the area, is a radon-cover installed over the sump pit?
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Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
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Septic Tank Capacity vs Usage in Daily Gallons of Wastewater Flow, calculating required septic tank size, calculating septic tank volume from size measurements
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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