Step-by-step

1
Mount the secondary 12V backup pump in the sump pit alongside the primary AC pump, slightly higher so it only runs if the primary fails or is overwhelmed.
2
Cut and fit the backup pump's discharge PVC into the existing line with its own check valve.
3
Set the marine deep-cycle battery nearby on a shelf or tray, off the floor.
4
Wire the backup pump to the battery through the smart dual-battery charging controller.
5
Plug the controller into a standard outlet so it trickle-charges the battery and keeps it topped off.
6
Test by unplugging the primary pump and pouring water in — the backup should kick on automatically.

Common mistakes

• Mounting the backup float at the same height as the primary
• Skipping a dedicated check valve on the backup line
• Letting the battery sit on a damp floor

Maintenance & next steps

Test the backup every few months and replace the deep-cycle battery about every 3 to 5 years.

When to call a professional

For dedicated circuit work, a whole-home battery, or if the pit needs to be enlarged.

Editor's note: This is instructional content for How to Set Up a Battery Backup System for a Sump Pump. Replace with your own firsthand experience and photos before publishing.

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