What should I look for when buying battery backup & combination sump pump systems?

A battery backup is non-negotiable for finished basements. The cost ($150-300) is trivial compared to flood damage. Test the backup monthly by unplugging the primary and pouring water into the pit. Marine deep-cycle batteries last 3-5 years. Mark the installation date and replace proactively.

What are common mistakes when buying battery backup & combination sump pump systems?

Skipping backup because the power rarely goes out. It only takes one extended outage during a storm. Not testing the backup regularly. A dead battery during a power outage is the same as no backup. Using a car battery instead of a marine deep-cycle. Car batteries are not designed for repeated deep discharge.

Battery Backup & Combination Sump Pump Systems

Overview

Power outages happen during storms -- exactly when you need your sump pump most. A battery backup sump pump activates automatically when the primary pump fails or power goes out. Combination systems include both primary and backup in one package. This is the single most important sump pump add-on for any home with a finished basement.

What to Know

Standalone Battery Backup

A second pump that sits in the same pit as your primary pump. Connected to a marine deep-cycle battery and charger. When the primary fails or power is out, the backup activates automatically via its own float switch. Runs 6-24 hours on a full charge depending on water volume and battery size.

Combination Systems

Primary and backup pump in one package with a shared controller. The controller manages both pumps: primary for normal operation, backup for power failure or primary pump failure. Some combinations also activate the backup during high-volume events when the primary cannot keep up alone.

Water-Powered Backup

Uses municipal water pressure to power a venturi pump -- no battery needed. Pros: unlimited runtime during power outages (as long as city water flows). Cons: uses 1 gallon of city water for every 2 gallons pumped, increases water bill, requires adequate municipal pressure (40+ PSI). Not available on well water.

Buying Tips

A battery backup is non-negotiable for finished basements. The cost ($150-300) is trivial compared to flood damage.
Test the backup monthly by unplugging the primary and pouring water into the pit.
Marine deep-cycle batteries last 3-5 years. Mark the installation date and replace proactively.
A high-water alarm ($15-25) provides an additional safety layer -- alerts you if both pumps fail.

Common Mistakes

Skipping backup because the power rarely goes out. It only takes one extended outage during a storm.
Not testing the backup regularly. A dead battery during a power outage is the same as no backup.
Using a car battery instead of a marine deep-cycle. Car batteries are not designed for repeated deep discharge.
Assuming a generator replaces a backup pump. Generators need fuel and manual start -- a backup pump is automatic.

Bottom Line

Every sump pump needs a battery backup. Combination systems are the easiest to install. Test monthly. Replace the battery every 3-5 years. The $150-300 investment prevents thousands in potential flood damage.