Backup Sump Pump Works

At Pumps Selection


Discover how Backup Sump Pump works so you can make a better selection of best sump pump suited for your pumping needs.  Here are the highlights.

  • There are many power sources that can be used. How does each work? Is there a best?
  • Charge strength varies. 
  • There are many different backup float-switch triggers. How dependable are they? 
  • Thermoplastic and cast iron are the most common type of construction material used. 
  • Operation capacity varies for backup sump pumps; however they do not have the same pumping capability as primary submersible sump pumps do.
  • Alarm Notification is provided by all battery backup sump pump systems.
We have applied backup sump pump works to application scenarios to help you hake the best selection for your pumping need.   See application scenarios.

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Review by Comparison

Here are the details of how backup sump pumps work.

Power Source

The following power sources that can be used for backup power.

Batteries are used for battery backup sump pumps.



Water Pressure is used for water powered sump pumps.



A portable generator can be used as power for backup sump pumps.



Automatic start standby generators can be used for primary submersible sump pumps.


Each of the power sources has its advantages and disadvantages.

See details at sump-pump-backup-power.

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Charger Strength

This term applies to batteries used as the source of power.

The higher the charger strength the faster the battery will be recharged after usage.



Charger strength varies from.4 to 20.


See details at battery-back-up-sump-pump-battery-charger-amps.



Each backup system has a trigger that activates the non electrical power source to begin operation.

What are the different triggers?

For battery powered and water powered backup sump pumps, water raises the float and the pump is activated into operation.


An automatic start standby generator is activated when the transfer switch

senses a utility power interruption.


A portable generator becomes operational when a human starts it.

Each of these triggers has advantages and disadvantages. See details for backup-sump-pump-float-switch-triggers.

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Materials Used in Construction

Thermoplastic: Outer casing is made of a hard, durable plastic.


Cast Iron and Stainless Steel: The outer casing and bolts are made of metal.


What are the advantages and disadvantages of the different materials?

Thermoplastic weighs less and is cheaper.


Cast iron and stainless steel lasts a lifetime, weighs more and is constructed to handle heavy duty usage.  This material is more expensive.


See details for battery-back-up-sump-pump-construction.




Operational Capacity

Backup sump pumps do not have the same operational capacity (pumping capacity) that primary submersible sump pumps do.

See battery-backup-sump-pump-gallons-per-minute and water-powered-sump-pump-gallons-per-minute to compare pumping capacity,
Dimensions of Backup Sump Pump and Pit

Each backup sump pump has unique measurements.

A sump pit with an 18"diameter basin or larger provides the greatest flexibility in being able to fit a primary and a backup sump pump into the pit.


A tether float requires a larger diameter-based pit than a vertical float

Size of Discharge Port Diameter 

The size is either 1 ¼ or 1 ½ inches in diameter.

Most backup pumps have an adapter to accommodate either size of PVC piping.


What are the advantages and disadvantages of the different sizes?

The capability to adapt to either a 1 ¼ or 1 ½ inch size PVC pipe is extremely beneficial.

A size of 1 ½ inches is required to handle heavy volumes of water.


Protection against Debris, Sludge, or Spherical Solids

Backup pumps use screens to protect against particles.



Those with the additional protection of float cages are built so the cage bottom concaves causing particles to run off.


Alarm Notification

Each of the battery backup sump pump systems have audible alarms that sound when the battery is activated when backup sump system is running. The alarm also sounds when the battery is discharged.

The Basement Watchdog Backup series also has an audible alarm when the battery fluid levels are low.

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Using the Basics to Understand Which Backup Sump Pump is Best for Your Situation.

  • Are you concerned about other household circuits, experience electricity failure frequently and for long periods of time, and have no ordinance limitations regarding the placement of a 48" (L) x 25" (W) x 29" (H) box outside your home? The automatic start standby generator can provide the most reliable power for a backup sump pump system as well as other household items.
  • Are you concerned about the expense of using water provided from municipal water source? Water powered backup systems only work with a municipal water source not a private well sources. It takes 1 gallon of municipal water to pump out 2 gallons of sump pit water.
  • Are you concerned about backup sump pump float-switch failure during operation? The Watchdog Big Boy, Watchdog Special and Watchdog Emergency Backup systems have a vertical dual float switch. If one float-switch fails the second one begins operation. The float-switch mechanism can also be replaced without removing the backup pump from the pit.  Wayne, Little Giant and Zoeller use vertical switches which are more reliable than the tether floats used by Simer Ace in the Hole and Flotec.
  • Are you concerned about removing the entire pump from the pit when the switch must be replaced?? The Basement Watchdog Sump Pump switch is external to the pump cage.  There is no need to remove the pump from the pit.  The switch is replaced by loosening the band holding the switch to the discharge PVC pipe, raising the switch out of the pit, replacing the switch, lowering it back down and tightening the band to the discharge PVC pipe.
  • Are you concerned with time required to recharge the battery after usage? The Watchdog Big Dog provides the quickest recharging. It has a 20 amp charger. Little Giant and Simer Ace in the Hole have 2 to 3.5 amp charger
  • Are you concerned about your current pump being able to handle the volume of water from heavy rain storms? If your sump pit is 18" in diameter, think about placing two 6" diameter Watchdog Basement Sump Pumps in the base of the pit.  Placing two dual switch Basement Watchdog Primary Sump Pumps in the pit could give you added peace of mind.  You would have four operational switches.  
  • Are you concerned about notification of battery depletion or failure? All major brands include this feature. Watchdog Backup systems provide the most detailed warnings regarding the battery backup system.
  • Is a warranty important? Wayne offers the longest warranty of three years.  The others are one or two years.
  • Are you concerned about how many continuous hours the battery will run? The continuous run time for all the major brand battery backup sump pump systems is within the range of six to nine hours. Simer Ace in the Hole runs continuously for six hours; Little Giant runs for nine hours; Wayne, Zoeller and Watchdog run for approximately seven hours.
  • Are you concerned your sump pit diameter is too small? The Watchdog pumps have the smallest width (9") and require only 1" additional for the vertical switch.  In many cases backup sump pumps are installed on top of the primary sump pump so size is not as much of an issue.
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