Do you need a backup sump pump? Will your sump pump ever fail? It is guaranteed to fail during a power outage, unless you have a battery backup.
Sooner, or most likely later, your sump pump will fail. Reasons other than a power outage for your sump fail are: the motor will wear out over time; the water level switch may fail; the pump might get clogged; or there simply may be an electrical short circuit. The problem is that the first indication of a sump pump failure is a flooded basement.
So what do you have stored in your basement that you care about? Have you extensively remodeled your basement? Will your insurance cover your sump backup? (Probably not.) Flooded basements can be costly.
The answer to this potential crisis is a backup sump pump. Backup pumps are generally installed in tandem with the the main pump. The water level indicator is set at higher level than the trigger water level for the main sump. So the main sump pump always removes the water before the backup pump is triggered. If the main pump fails, the water level will rise above its trigger point, and reach the trigger point for the emergency backup sump pump. Then this pump takes over, until the main pump is repaired or replaced.
One of the main reasons for a sump pump to fail is a power outage. It is for this reason that you should have a battery powered back up sump pump. A battery powered sump pump does not require the electrical grid to work. It does however require the electrical grid to keep the battery charged. The battery on this type of pump is a maintenance item. You need to ensure that it is charging correctly and will be charged and ready in the time of an emergency. Batteries also need to be replaced every few years.
Another option is a water-powered backup system. This type of system requires no battery or electricity. It uses pressurized water to flow over a small opening connect to a hose going into the pit. Suction produced by the flowing water over the hole pulls water up out of the pit.
Sufficient water pressure of 40 pounds per square inch is required for this system to work. Typical municipal water services are usually reliable and sufficient enough for this type of backup sump pump. Be aware though that it takes two gallons of municipal water to remove one gallon of sump water.
Even with a backup system, you may get additional peace of mind if you invest in a sump pump alarm. The alarm will alert you to any high water condition, for example, when your sump system is malfunctioning.