The most common reason a sump pump will not turn on is a float switch that is stuck — blocked by debris in the pit, jammed against the pit wall, or corroded after sitting in a damp environment for years. Confirming the pump has power comes first, since a float switch problem only matters once you know electricity is actually reaching the unit.
Check power first
Before troubleshooting the float switch, confirm the pump is actually receiving power. Check that it is plugged in (sump pump cords can work loose over time), that the outlet itself has power, and that the breaker feeding that circuit has not tripped. A GFCI outlet, common on sump pump circuits, can also trip independently of the main breaker — check for a reset button on the outlet itself.
Test the float switch
- Unplug the pump before testing
Always disconnect power before reaching into the pit.
- Manually lift the float by hand
It should move freely up and down through its full range of travel without catching on anything.
- Plug the pump back in and lift the float again
If lifting the float by hand triggers the pump to run, the switch itself is functional and the problem is something restricting its normal movement in the pit.
- If lifting the float does nothing
The switch itself has likely failed electrically and needs replacement rather than further adjustment.
Clear debris from the pit
Dirt, small stones, and general sediment collect in a sump pit over time and can physically block the float switch’s movement, sticking it in either the on or off position. This is the most common single cause of a float switch that seems to have failed but has not — clearing the pit and confirming free movement resolves it without any parts needed.
Check for corrosion
Sump pumps sit in a damp, often standing-water environment for years at a time, which makes corrosion at electrical connections and moving parts a genuine long-term risk. Look for visible rust or corrosion at the switch’s connection points and wiring, since corrosion can break the electrical circuit even when the float itself still moves freely.
When the switch needs replacing
| Test result | What it means |
|---|---|
| Float moves freely, lifting it triggers the pump | Switch is functional — find and clear what was restricting movement |
| Float is stuck or restricted | Clear debris; retest before assuming the switch has failed |
| Float moves freely but lifting it does NOT trigger the pump | Switch has failed electrically and needs replacement |
| Visible corrosion at wiring/connections | Replace the switch even if it intermittently works — corrosion tends to worsen |
When to call a professional
If the pump does not run even when tested directly on a known-good outlet (bypassing the float switch entirely, which some pumps allow via a direct plug-in test), the pump motor itself may have failed rather than the switch — at that point, replacement of the whole unit is usually more practical than a motor-level repair, given how affordable sump pumps are relative to labour costs.
Stop and call a qualified appliance technician or electrician if you find scorched or melted wiring, smell burning, see water that has reached electrical components, or if the fault returns immediately after a repair. Never bypass a safety device — thermal fuses, door interlocks and flood switches fail for a reason, and defeating one converts a broken appliance into a fire or flood risk.
