Why does my sewage ejector pump keep tripping the breaker?

Turn the power off and leave it off. Liberty Pumps, a maker of sewage ejector pumps, puts it this way: "Always disconnect pump(s) from power source(s) before handling or making any adjustments to either the pump(s), the pump system, or the control panel." Zoeller's instructions say to shut off the breaker first and then unplug the pump. They add a warning about standing water: "Under flooded conditions, contact your local electric company or a qualified licensed electrician for disconnecting electrical service prior to pump removal."

Never reach into a wet basin or a damp floor to reset a plug. Liberty warns: "Do not handle or unplug the pump with wet hands, when standing on damp surface, or in water unless wearing Personal Protective Equipment." If there is water on the floor around the pump or the panel, stop and call.

Then protect the house. While the pump is off, sewage from your basement fixtures has nowhere to go. Go easy on toilets, showers and the washer until the pump runs again. Many systems also carry a high-water alarm. Liberty notes that the Uniform Plumbing Code "states that sewage systems shall have an audio and visual alarm that signals a malfunction of the system, to reduce the potential for property damage." If the alarm is sounding, that is your signal that the basin is filling.

Liberty's troubleshooting chart for its LE-series sewage pumps has a row for exactly this problem, "Repeated tripping," with these causes and fixes:

• "Circuit protection underrated." The fix: "Check rating and replace with proper size." The proper size is the one that matches the pump's nameplate, not a bigger breaker to stop the nuisance.
• "Other appliance on same circuit." The fix: "Pump requires separate circuit." Zoeller says the same about the branch circuit: "A separate branch circuit is recommended," sized according to the National Electrical Code for the current shown on the pump nameplate.
• "Pump is connected to an extension cord or wiring is inadequate or compromised." The fix: "Have an electrician check for proper wiring." Liberty's safety list warns that extension cords "can overload both the product and extension cord supply wires."
• "Improper voltage." The fix: "Have an electrician check all wiring for proper connections and adequate voltage and capacity."
• "Obstruction in pump." The fix: "Remove obstruction." A jammed impeller makes the motor work harder and pull more current.
• "Foreign matter buildup." The fix: "Clean motor housing."
• "Incorrect motor rotation." For a single-phase pump, Liberty says to contact the factory.

Zoeller's chart for its submersible pumps lists the same family of causes when a motor "overheats and trips overload or blows fuse": incorrect voltage, an impeller or seal bound mechanically, a defective capacitor or relay, or a shorted motor. How fast it trips is a clue. A pump that trips the instant it starts often has a short or a locked impeller. One that runs a while and then trips is more likely overheating. It may be on low voltage, or dragging on something.

Only the things you can see from outside the basin, with the pump unplugged and the breaker off. Look for an extension cord or power strip. Look at what else shares the outlet. Check whether the cord is cut, pinched or chewed. Do not open a sealed sewage basin to check the float. A stuck float is one of the things a plumber checks, and it can keep the motor running. Our page on replacing a sewage ejector pump float switch covers that part.

Write down what you notice before you call anyone. Does the breaker trip the moment the pump starts, or after it has run a while? Is it a breaker or a GFCI outlet that trips? Did anything else on that circuit go out? Did the pump make any unusual noise first? Liberty's troubleshooting chart lists them together as one cause: "Tripped circuit breaker, tripped GFCI, blown fuse, or other interruption of power." A GFCI trip and a breaker trip can point to different faults (current leakage versus overload), so tell the electrician which one it was. Those details save the electrician and the plumber a lot of guessing.

Do not open the pump, and do not go into the basin. Liberty's manual says "Do not enter a pump basin after it has been used. Sewage and effluent can emit several gases that are poisonous." Liberty also warns that "Sewage and effluent systems produce and may contain flammable and explosive gases." Our page on sewer gas and methane explains the risk. Removing a clogged pump, cleaning an impeller and testing a check valve are jobs for a plumber with the right protective gear.

Send the electrical part to a licensed electrician. That means a shared or undersized circuit, a cord that is not up to the job, low or wrong voltage, a breaker of the wrong size, and any direct wiring into a panel or junction box. Liberty's own manual covers a single-phase pump wired directly into a control device or junction box, where the plug has to come off. In that case, "a certified electrician shall complete the wiring in accordance with the National Electric Code and applicable local codes." It also says "Licensed electrical personnel should be present when the panel or breaker is energized for the first time."

Send the pump side to a plumber: a jammed impeller, a stuck float, a failing motor or a discharge problem. The plumbing code treats the pump as part of the drainage system. The 2024 International Plumbing Code says drains that cannot flow to the sewer by gravity must be "discharged into a tightly covered and vented sump from which the liquid shall be lifted and discharged into the building gravity drainage system by automatic pumping equipment or other approved method." If you are unsure which side is at fault, start with the electrician for the breaker and bring in the plumber once the circuit checks out.

Once the cause is fixed, test before you walk away. Liberty says to "Verify operation of the pump, floats, and alarm circuits" and to "Run several cycles of water through the system to verify correct control operation for the installation." A pump that starts, empties the basin and stops on its own, without tripping, is the result you want.

HQ Plumbing & Air is licensed and insured, and our residential plumbing service covers the plumbing side. We give a free estimate, and you get the price up front before work starts. We take emergency calls 24/7. If sewage is already backing up, see what to do about sewage backing up into a tub or shower.

For how a sewage pump differs from a sump pump, see sump pump vs ejector pump vs lift station, or the sewage ejector pump glossary entry.