Sump Pump Battery Backup: What to Check Before Buying

What to compare

• Pumping capacity at your lift height: look for gallons per hour at 10 feet (or your actual lift), not the "zero-foot" figure.
• Run time: how many hours or gallons on a full charge. Larger batteries run longer.
• Battery type: sealed (AGM or maintenance-free) batteries need less upkeep than flooded batteries that need water added.
• Charger and monitoring: a smart charger, battery health display, audible alarm and phone alerts.
• Separate float switch: the backup should turn on independently of the main pump.
• Fit: room in the sump pit for both pumps and a check valve on each discharge line.

Water-powered backups

Some backups use city water pressure instead of a battery, so they keep running during long outages. They use household water while running, need adequate water pressure, do not work with most private wells, and local plumbing codes may require a backflow preventer. Ask a plumber whether one fits your home.

Cost and upkeep

• A sump pump system with battery backup averages about $1,220 installed, according to HomeAdvisor.
• Batteries wear out over a few years; note the install date and test the system a few times a year.

See sump pump replacement cost for primary pump options.