Best Sump Pump Battery Backup Systems for Power Outages

It depends on battery size and how much water comes in. Wayne rates its WSS30VN at up to 10,000 gallons on one charge of a 75 Ah battery, so a pit taking in 200 gallons an hour would last about 50 hours. Basement Watchdog lets you connect two batteries in parallel on the CITS-50 for double the runtime.

A 12V deep-cycle battery, either a wet cell or a maintenance-free AGM type; none of these systems include one. Higher amp-hour ratings pump more gallons per charge, and Wayne specifies its 75 Ah WSB1275 for the WSS30VN.

Time how fast your pit fills in heavy rain and compare that to the backup's rating at 10 ft of lift. A pit that takes on 10 gallons every 2 minutes needs 300 GPH, which the 1,500 to 2,300 GPH backups here cover several times over. Use the 10 ft rating, because flow drops as lift rises: the Basement Watchdog BWSP moves 2,500 GPH at 0 ft but 1,730 GPH at 10 ft.

Yes if your pump runs during storms, because power outages and heavy rain tend to come together. A backup also covers a stuck float or failed primary pump. Standard homeowners policies usually exclude sump overflow damage unless you add a water backup endorsement, so the pump is often your only protection.

A water-powered backup uses city water pressure instead of a battery, so it never runs down but needs municipal water and a backflow preventer. Homes on a well cannot use one, because the well pump stops in an outage. A battery backup works on any home but is limited by battery capacity.

Most homeowners can install a preassembled combo; Wayne says its WSS30VN drops in within 15 minutes with no weep hole to drill. An add-on unit needs a tee and check valve on the discharge pipe. Both need a grounded outlet near the pit for the charger.

Yes, but someone has to be home to start and refuel a generator. A typical 1/3 HP sump pump draws about 800 W running and up to about 2,000 W starting, and a 1/2 HP pump about 1,050 W running and 2,500 W starting. A battery backup switches on by itself, which is why it is the safer choice for an empty house.

Choose an add-on if your current pump works and the pit has room for a second pump. Choose a combo if the primary is due for replacement, since you get a new primary and backup on one plumbed assembly. Check pit size: the Wayne WSS30VN needs a basin 16 inches or wider.

Test it at least every few months by unplugging the primary pump and filling the pit with a bucket of water until the backup starts. Check the controller lights after every test; the Basement Watchdog controllers show what needs attention, and the BWSP also monitors battery fluid. Top up wet-cell batteries with distilled water as needed.

Sealed standby batteries are typically replaced every 3 to 5 years, sooner if they go through many deep discharges. The controllers on the Basement Watchdog systems warn you when the battery is weak, and the Wayne ESP25 sounds an alarm when the backup is running so you know the battery is being used.