Backup Sump Pump Basics

Backup Sump Pump Basics

The following information is provided to help you understand backup sump pump basics (their features) and how to use the basic information to know which sump pump is best for your situation.

Scroll down to see the information.

To see detailed information for the battery backup and water powered sump pumps go to the site map on the right and scroll down.

Power Source

Battery provides the power to enable a backup sump pump plugged into it through the use of a wired housing case to perform the pumping cycle for the removal of the water from the pit. Twelve or twenty four volt battery power is used. The voltage and type of battery required varies by manufacturer.

Water Pressure provides the power to keep a backup sump pump running. The water used must come from a municipal source and have a pressure between 40 and 100 PSI (pounds per square inch).

A portable generator provides power through the conversion of gas or propane into energy. The pump must be plugged into the generator.

Automatic start standby generator provides the power when the sump pump is plugged into it.

What are the advantages and disadvantages of each power source?

Batteries require monitoring to make sure they are operational in the time of need. Most backup systems have an alarm that lets the owner know when a battery requires maintenance or replacement and is being used by the backup pump. Batteries are rechargeable.

Battery Case and AccessoriesWater power requires no batteries and has no moving parts. Operation of watered power systems requires a PSI water pressure between 40 and 100 PSI (pounds per square inch). Private well water cannot be used and the municipal provided water must have reliable water pressure. It takes 1 gallon of municipal water to remove 2 gallons of sump pit water so can be costly to operate.

Portable generator must be placed outside. It must be started manually. Most operate from gas or a propane tank.

Automatic start standby generator is expensive to purchase and install (four to ten times more expensive than battery power) but are very reliable. This type of generator runs off of natural gas or propane tanks and can provide power to multiple household appliances during power failure.

Charger Strength

This term applies when using batteries 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.


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

What are the different triggers?

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

For water powered backup sump pumps, when the float raises, a valve allows pressured water to flow down to the pump. The flowing of the pressured water activates the backup system into operation.

An automatic start standby generator is activated when the transfer switch senses a utility power interruption.

portable generator becomes operational when a human starts it.

What are the advantages and disadvantages of each trigger?

The transfer switch for the standby generator is the most reliable and quickest way to activate the operation of a backup system. The backup pump is operational as soon as the power goes out.

Battery and water powered systems are not activated until the water rises to the height of the float. That means water has already collected in the pit.


Batteries deplete and loose charge.

Municipal water pressure is not constant. A drop below 40 PSI means the backup system is not operational.

The float-switch mechanism, impeller or clogging of the backup sump pump plugged into a battery or standby generator source of power could fail.

The tether switch is not as dependable as the vertical switch.

Dual vertical switches offer twice the reliability.

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?
  • Thermo plastic 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.

Operational Capacity

What are the volumes at which backup pumps can discharge water?

  • Pumping capacity is measured by number of gallons per minute or hour at a specific rise.
  • Capacity is determined by size of motor and source of power.

What are the advantages and disadvantages of operational capacity?

  • Larger motors using battery or generator power move more water during operation.
  • Smaller motors move less water during operation and require less battery or generator power.
  • The amount of water moved during operation of a water powered backup sump pump is determined by the municipal water pressure. The greater the pressure the greater volume of water that is discharged. Generally water powered pumps have a lower operational 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.

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 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 ?” 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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