Troubleshooting Common Ejector Pump Failures and How to Fix Them

How Ejector Pumps Work

An ejector pump, also known as a sewage ejector pump, is a submersible pump installed in a basin below the main sewer line. It moves wastewater from lower-level plumbing fixtures—such as toilets, sinks, and washing machines—up to the municipal sewer or septic system. The pump is activated by a float switch or pressure sensor when the basin fills to a preset level. Understanding this basic operation is key to diagnosing failures because most issues stem from the pump's control system or the basin's condition.

The pump lifts wastewater through a discharge pipe fitted with a check valve to prevent backflow. If any component in this system fails, the pump may not operate correctly, leading to backups or overflows. Regular inspection of the float switch, check valve, and discharge line can prevent many common problems.

Common Ejector Pump Failures and Their Causes

1. Pump Won’t Turn On

This is one of the most frustrating failures, often caused by a simple power interruption. Check the following:

Power supply: Confirm the pump is plugged in and the outlet is live. Test the outlet with a multimeter or plug in a lamp. A tripped GFCI or circuit breaker may need resetting.
Float switch obstruction: The float must move freely. Debris, sludge, or a stuck float arm can prevent activation. Lift the float manually to see if the pump starts.
Control panel failure: In systems with an alarm panel, a blown fuse or faulty relay can interrupt power. Inspect the panel for error codes or burnt components.
Motor or capacitor failure: A burned-out motor or dead start capacitor requires replacement. Listen for humming—if the pump hums but won’t run, the capacitor may be defective.

2. Pump Runs Continuously

A nonstop pump quickly wears out and wastes electricity. Common reasons include:

Stuck float switch: If the switch is in the “on” position, the pump will run until the basin is empty. Check for physical jams or a float that has fallen off its track.
Clogged inlet or discharge pipe: Solid debris can block the pump’s intake, preventing it from moving water even though the motor runs. A clogged check valve may also cause the pump to recirculate water.
Faulty pressure sensor: Some pumps use a pressure switch instead of a float. A failed sensor may send a false “full” signal, keeping the pump active.
Excessive water inflow: A leaking fixture or groundwater infiltration can overwhelm the pump’s capacity, causing it to run continuously. Confirm the basin level drops when the pump operates.

3. Pump Cycles Frequently (Short Cycling)

Frequent on/off cycles strain the motor and can lead to premature failure. Causes include:

Float switch setting is too sensitive: Adjust the float’s range so that the pump turns on at a higher water level and off at a lower one.
Small basin or rapid water entry: If the basin is undersized or multiple fixtures discharge quickly, the level fluctuates rapidly. Consider a larger basin or a different switch type.
Sludge buildup: Accumulated grease, soap scum, and solids reduce the effective volume of the basin. Clean the basin thoroughly.
Faulty check valve: A failing check valve allows water to flow back into the basin after the pump stops, causing it to restart immediately. Replace the valve if it leaks.

4. Pump Runs but Doesn’t Pump Water

This indicates the motor is working but the impeller is not moving water efficiently:

Clogged impeller: Hair, wipes, or debris can wrap around the impeller. Remove the pump and clean the impeller housing.
Broken impeller or shaft: A cracked impeller or stripped shaft will prevent water movement. Replacement parts are often needed.
Air lock: Air trapped in the discharge line can stop water flow. Prime the pump by pouring water into the discharge pipe or installing a vent hole.
Discharge pipe frozen or blocked: In cold climates, ice can obstruct the pipe. Check for frost or external damage.

5. Pump Vibrates or Makes Unusual Noises

Noises often indicate mechanical issues:

Loose mounting: Vibrations can cause the pump to knock against the basin wall. Secure the pump with rubber grommets or a bracket.
Damaged bearings: Grinding or squealing sounds suggest bearing wear. Replace the pump or motor assembly.
Cavitation: When the pump runs dry or with low water, it can cavitate, making a rattling sound. Ensure the basin always maintains adequate liquid level.
Foreign object inside: Something hard (glass, metal) inside the volute will cause scraping. Disassemble and remove the object.

Step-by-Step Troubleshooting Guide

Tools and Safety Precautions

Before starting, gather:

Multimeter (for voltage and continuity tests)
Screwdrivers, pliers, and wrenches
Bucket and cleaning supplies
Replacement parts (float switch, check valve, capacitor)
Rubber gloves and protective eyewear

Always disconnect power to the pump before reaching into the basin or handling electrical components. For submersible pumps, unplug the unit or shut off the dedicated circuit breaker. Wear rubber gloves because sewage contains harmful bacteria.

1. Visual Inspection

Remove the basin lid and inspect the interior. Look for visible debris, a stuck float, or signs of water damage to electrical connections. Check the discharge pipe for cracks or leaks. Note any unusual odors that might indicate a broken septic line.

2. Test the Float Switch

Manually lift the float switch while watching the pump respond. If the pump starts, the switch is likely working, but the issue may be with the water level setting. For a tether float, ensure the cord isn’t twisted. For a vertical float, confirm the rod moves freely. If the pump doesn’t start when you lift the float, use a multimeter to test continuity across the switch leads. Replace the switch if it fails the continuity test.

3. Check Power at the Pump

With the pump plugged in, measure voltage at the pump cord’s plug or inside the control box. You should read 115-120 V (or 230 V for heavy-duty models). If you get no reading, trace the circuit: could be a tripped breaker, bad outlet, or faulty cord. Inspect the pump’s power cord for cuts or melting.

4. Inspect the Check Valve

The check valve (usually located on the discharge pipe) prevents backflow. Tap it gently—if you hear water sloshing back, the valve is stuck open. Remove and clean or replace the valve. A failed check valve causes short cycling and reduces pump efficiency.

5. Clear Blockages

Turn off power and disconnect the pump from the discharge pipe. Use a plumber’s snake or a hose to flush out the pipe. Clean the pump’s inlet screen and impeller housing. Reassemble and test with water in the basin.

6. Test the Capacitor and Motor Windings

If the pump hums but doesn’t start, the capacitor (if equipped) may be weak. Discharge the capacitor safely, then test with a multimeter set to capacitance mode. Compare the reading to the value printed on the capacitor. A capacitor that’s more than 10% off should be replaced. Check motor winding resistance between the power leads—an open circuit indicates a burned-out motor.

When to Repair vs. Replace

Some repairs are straightforward, but if the pump is over 8-10 years old, replacement may be more cost-effective. Consider replacing the pump if:

The motor or housing is cracked.
Electrical failures recur after repairs.
The pump uses obsolete switches or parts are hard to find.
You experience frequent clogs due to undersized unit (check the pump’s horsepower: 1/2 HP may be insufficient for high-volume use).

Investing in a higher-quality pump with a wider impeller and better float switch can prevent future headaches. Look for models with a cast-iron housing and stainless steel hardware for durability.

Preventive Maintenance Schedule

Routine care extends the life of your ejector pump and reduces emergency calls. Follow this schedule:

Frequency	Task
Monthly	Lift and test the float switch manually. Listen for unusual noises while the pump runs.
Quarterly	Remove the basin lid and inspect for debris, sludge, or grease buildup. Clean the inlet screen.
Annually	Have a professional inspection of the pump, check valve, and discharge line. Replace the check valve every 3-5 years.
Every 5 years	Consider replacing the pump as a preventive measure, especially in high-demand residential or commercial settings.

Additional Tips

Never flush wipes, feminine products, or grease down drains—these are the leading cause of clogs.
Install a high-water alarm to alert you before a backup occurs.
Keep the pump’s electrical cord dry and off the basement floor to prevent damage.
Test your sump pump / ejector pump system after heavy rain to ensure it handles surge flow.

When to Call a Professional Plumber

Some situations require licensed expertise:

Repeated failures despite following troubleshooting steps.
Electrical issues beyond a simple reset—frayed wires, burned control panels, or GFCI that won’t hold.
Discharge pipe damage underground or inside walls.
Backup into the house—this indicates a serious blockage or pump failure that needs immediate attention.
Installation of a new system or upgrading to a larger basin/pump to meet code requirements.

Professional plumbers can also perform dye tests to detect groundwater infiltration, which may overload the pump. They have specialized tools like video cameras to inspect discharge lines for blockages you can’t reach.

Understanding Local Plumbing Codes

Many municipalities have specific requirements for ejector pump installations. For instance, the International Plumbing Code (IPC) mandates that sewage ejector basins be vented and that pumps be capable of handling solids up to 2 inches in diameter. Check your local building department for guidelines. Non-compliant installations can result in fines or liability if a backup damages property.

For commercial installations, the NFPA 820 standard may apply to ensure fire safety in pump rooms. Always consult a professional if you are unsure about code compliance.

Conclusion: Keep Your System Running Smoothly

Troubleshooting ejector pump failures doesn’t have to be daunting. By understanding the common causes—float switch malfunctions, clogs, electrical issues—you can often resolve problems yourself. Routine maintenance and prompt attention to unusual behavior will extend the pump’s life and protect your home from sewage backups. When in doubt, call a qualified plumber. A properly maintained ejector pump is a silent workhorse that keeps your below-grade living space dry and sanitary.

For further reading, refer to the Plumbing Manufacturers International for product standards or consult your pump’s manual for specific troubleshooting diagrams. If you are in the market for a replacement, consider models from reputable brands like Zoeller, Liberty Pumps, or Wayne—all of which offer detailed support documentation online.