Last Updated on September 1, 2026 by Anta Plumbing Master Plumber
Yes, if you rely on a primary sump pump to keep your basement dry, you absolutely need a backup power source. A primary sump pump operates on standard household electricity. When severe weather knocks out the hydro grid, the primary pump stops working entirely, allowing rising groundwater to overflow the pit and flood your basement without any mechanical resistance. A battery backup keeps your waterproofing system running during these critical outages.
| System Type | Power Source | How It Operates | Limitations |
| Primary Sump Pump | Standard electrical grid | Handles all water removal under normal conditions. | Instantly useless during a power outage. |
| Battery Backup System | Deep-cycle marine or AGM battery | Automatically kicks in if the main power fails or the primary pump breaks down. | Batteries lose capacity over time and must be replaced every 2 to 6 years. |
| Water-Powered Backup | Municipal water pressure | Uses city water pressure to generate suction and pump water independently of the electrical grid. | Performance drops if municipal water pressure drops during droughts or main breaks. |
How a Battery Backup System Works
A battery backup system is installed directly in the sump basin alongside or above your primary pump. During normal operation, the primary pump handles the drainage while an active wall charger maintains the backup battery at full charge.
If the power fails and the water level continues to rise, a secondary float switch triggers the backup pump. It draws power from an independent battery (usually a sealed Absorbed Glass Mat or lead-acid marine battery) and pushes the water clear of the foundation.
Expected Runtime: A standard 75 amp-hour battery cycling every 3 to 5 minutes provides approximately 5 to 10 hours of flood protection. A higher-capacity 100 amp-hour battery extends that protection window to 7 to 12 hours.
Signs You Need a Backup System Immediately
- Your property frequently loses power during heavy spring rainstorms or rapid winter snowmelts.
- You have a finished basement where flooding would destroy drywall, flooring, or personal property.
- Your primary pump runs constantly during heavy rain, meaning it is working at maximum capacity and is highly vulnerable to mechanical failure.
- Your home uses a backwater valve fitted on the main sewer line to stop municipal sewage backup, but has no defence against groundwater during a power loss.
The City of Toronto now subsidizes both the pump and the battery backup under its flood protection program, so check what the rebate covers before you buy. We handle sump pump installation and battery backup wiring across Toronto and Oakville, permits and rebate paperwork included.
