If your sump pump won’t turn on, the most common culprits are a stuck float switch, a dead outlet or tripped breaker, or a failed pump motor. Homeowners can rule out the first two without touching the pump. The third usually means a replacement is coming, and that’s a job for a licensed plumber.
Start With the Outlet, Not the Pump
Before assuming the pump is dead, check the power. Sump pumps plug into a standard 120V outlet, typically a GFCI outlet in the basement near the pit. GFCI outlets trip without tripping the breaker, so the circuit panel can look fine while the outlet is completely dead.
Press the reset button on the outlet face. If it clicks and power returns, you found your problem. If the outlet won’t reset, or if the pump is hardwired, check the breaker panel for a tripped breaker.
Sump pumps should be on a dedicated circuit. If yours shares a circuit with other basement equipment, that shared load can cause nuisance trips. Reset the breaker once. If it trips again immediately, stop and call a licensed electrician.
The Float Switch Is the Most Common Failure Point
The float switch is a small plastic device that rises with the water level and triggers the pump. When it works, you barely know it exists. When it fails, the pump sits there doing nothing while water fills the pit.
Two things go wrong with float switches. The float can get physically stuck against the pit wall, tangled in the pump cord, or sitting at an angle that keeps it from rising. You can check this: look into the pit with a flashlight and see if the float is hung up on anything. A float that moves freely up and down is probably functional.
The switch itself can also fail electrically. Contacts corrode or wear out over time. Distinguishing a bad float switch from a failed motor requires a multimeter and hands-on electrical experience. If that’s not in your skill set, this is where you call a plumber.
What a Plumber Actually Diagnoses
A licensed plumber works through the same logic, just faster and with the right tools.
They’ll verify power at the outlet with a meter, not just by looking. They’ll test the float switch separately from the pump, check voltage at the motor terminals, and measure current draw. If the motor is pulling high amperage without moving water, the impeller is jammed or the windings are failing.
They’ll also check things that aren’t obvious from the outside. The check valve above the pump can fail and let water drain back into the pit after each cycle, forcing the pump to short-cycle and eventually burn out the motor. The discharge line outside can be frozen or clogged, creating back-pressure that causes overheating.
A pump that hums but doesn’t spin almost always has a seized impeller or a failed start capacitor. A pump that makes no sound at all has a power problem or a dead motor. Neither is a DIY fix.
What You Can Safely Check Yourself
These checks are reasonable for any homeowner:
- Press the reset button on the GFCI outlet near the pit.
- Check the breaker panel and reset a tripped breaker (once only).
- Look into the pit with a flashlight and see whether the float is wedged against the pit wall or caught on the pump cord.
- Confirm the pump is sitting flat on the pit floor and hasn’t tipped over.
- Confirm the discharge line outside the house isn’t capped, frozen, or clearly blocked.
Stop there. Anything beyond visual checks or a single breaker reset involves pump internals or electrical connections, and that’s plumber territory.
When to Call a Pro
Call a licensed plumber if:
- Resetting the outlet and clearing an obvious float obstruction doesn’t get the pump running.
- The breaker trips more than once.
- Water is rising and the pump isn’t keeping up.
- The pump runs continuously or short-cycles rapidly.
A stuck float switch is a cheap fix. A failed motor usually means a new pump. Either way, it’s better to know during a dry period than during the first heavy rain of the season.
If you’re in California, verify your plumber’s license at cslb.ca.gov before work starts. Plumbing work requires a C-36 license. It takes 30 seconds to check.