Sump Pump Won't Turn On
Updated February 20, 2026
Basement flooding emergency waiting to happen. Usually electrical (tripped breaker, unplugged cord, GFCI), mechanical (stuck float), or burned-out motor. Diagnosing takes minutes and prevents thousands in water damage.
Overview
One of the most urgent situations a homeowner can face. No protection against flooding. Few inches of standing water: thousands in damage. Good news: most common causes are simple. Tripped breaker, unplugged cord, tripped GFCI, stuck float -- fixable in minutes. Burned-out motor is less common but means replacement. Start with power, then float, then motor.
Symptoms
- Water rising in the pit and pump not activating -- immediate action needed
- No sound at all when water is above the float -- no hum, no vibration. Power issue or dead motor.
- Hums but does not pump -- impeller jammed by debris or seized bearing, or capacitor failed
- Float stuck down, will not rise -- snagged on debris, pipe, pit wall, or power cord
- Worked last time, will not activate now -- power interruption, float obstruction, or motor failed since last use
- GFCI outlet tripped -- test/reset buttons show tripped state, no power to the pump
Common Causes
- Tripped breaker or GFCI -- most common cause. GFCI trips from moisture, surges, or age. Can go unnoticed for months until the pump is needed.
- Unplugged cord -- accidentally disconnected during storage, cleaning, or nearby work. Piggyback plugs can partially separate, breaking the circuit.
- Stuck float -- tangled on discharge pipe, caught on pit wall, snagged on debris. Cannot rise, pump never gets the on signal even as water floods.
- Burned-out motor -- 7-10 year lifespan. Burns out from age, dry running, surges, or overwork. No hum, no vibration, no response. Replacement needed.
- Frozen discharge -- pump runs briefly then trips thermal overload. Will not restart until cool. Appears dead but is actually protecting itself from a blocked line.
What You'll Need
How to Fix It
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Check the Power Supply First
GFCI outlet? Press reset firmly. Breaker panel: tripped breaker? Full off then back on. Cord fully plugged in? Piggyback plugs firmly connected? Pour water into the pit to test. Breaker trips again immediately? Short circuit -- stop resetting.
Warning: Breaker trips repeatedly? Do not force it. Short circuit or ground fault -- fire and electrocution hazard. Call an electrician or plumber. -
Test the Pump Motor Directly
Power confirmed but pump dead? Piggyback plug: unplug both, plug just the pump plug (bypasses the float). Runs? Motor is good, float is the problem. No sound or vibration? Motor is dead, replace the pump. Hums but does not spin? Jammed impeller or failed capacitor.
Tip: Bypassing the float? Only run a few seconds without water. Dry running overheats the motor. Pour water in first if possible. -
Free the Float Switch
Motor works but pump does not activate? Float. Unplug, inspect for tangles, obstructions, mineral buildup, damage. Free it, confirm full range of motion. Tether too long? Shorten. Vertical float? Vinegar to clean minerals, ensure it slides freely. Test with water.
Tip: Unreliable float? Replace. Vertical floats tangle less than tethered. Electronic (solid-state) switches have no moving parts -- most reliable ($30-50 vs $10-20 mechanical). -
Clear a Jammed Impeller
Hums but no pumping? Unplug, remove from pit. Check intake screen and impeller for gravel, stones, deposits. Clear obstructions. Spins freely by hand? Reinstall and test. Frozen by corrosion or seized bearing? Replacement needed.
Warning: Always unplug before hands near the impeller. Float activation or power surge could start it. -
Check the Discharge Line
Turns on briefly then quits? Discharge frozen or blocked. Check exit point for ice, snow, mud, debris. Thaw with warm water, not flame. Thermal overload tripped? Let it cool 15-30 minutes, should restart once discharge is clear.
Tip: Freeze-relief fitting near the foundation wall. Port opens automatically if the main discharge freezes, letting water escape at ground level. -
Replace the Pump (If Motor Has Failed)
Motor dead? Replace. Unplug, disconnect discharge, remove from pit. Clean the pit. New pump flat and level, connect discharge (same size). Plug in, pour water, confirm activation, pumping, and clean shutoff. Check connections for leaks.
Tip: Match or exceed the old pump's GPH at the same head pressure. Old one undersized? Upgrade now. Cast iron: quieter, more durable. Install a battery backup at the same time for critical applications.
When to Call a Pro
Call a plumber or electrician if the breaker trips repeatedly (short circuit), if you are not comfortable with electrical, if the pump needs professional sizing and installation, if the discharge is buried or needs rerouting, or if the pit is flooding and you need emergency pump-out service.
Prevention Tips
- Test every 3-4 months: pour water, watch a full cycle. Single most important prevention.
- Check GFCI and breaker monthly. Tripped state can go unnoticed for months.
- Battery backup pump. Activates automatically during primary failure or power outage. 5-10 hours on a charge.
- Sump pump alarm ($15-25). Sounds when water rises above the activation point.
- Pit clean, float area clear. Inspect both every time you test.
- Replace every 7-10 years proactively. Dormant pump may fail on its first heavy rain event.