What causes a well pump to hum but not pump?

A well pump humming but not pumping usually points to an electrical, mechanical, or water-supply problem that needs prompt attention before the pump burns up or the system loses prime.

Well pump humming but not pumping: the most common causes

When a pump hums, the motor is getting power, but something is keeping the pump from starting or moving water. In Central Florida wells, we see this with jet pumps, submersible pumps, pressure tanks, and irrigation pumps.

Common causes include:

• Bad start capacitor or control box on the motor
• Stuck impeller from sand, scale, or debris
• Low voltage or electrical failure
• Pressure switch problems
• Loss of prime on a jet pump
• Failed motor bearings
• A pump that is too worn out to start under load
• Well or suction-side issues that prevent water from reaching the pump

If the pump hums for more than a few seconds without moving water, shut it off and call. Letting it sit energized can overheat the motor.

Electrical issues are a major cause

A humming sound often means the motor is trying to start but cannot. On many systems, that can be a failed capacitor, a bad control box, a broken wire, or a pressure switch that is not sending the right signal.

Electrical problems can be simple on paper and dangerous in practice. We do not recommend opening electrical components yourself. If your pump is humming, call a licensed well contractor who works on the full system, not just one part of it.

Why a humming pump may not move water

A pump can run without pumping if the internal parts cannot spin freely or if the pump cannot create enough suction or pressure. In our area, that can happen because of Florida groundwater conditions, sediment, or age-related wear.

Mechanical blockage or worn parts

Inside the pump, the impeller is what moves water. If it is jammed, cracked, or worn down, the motor may hum but the pump will not produce flow.

We also see:

• Sand or grit lodged in the pump
• Rust or mineral buildup
• Seized bearings
• A failing shaft or motor assembly

When this happens, repair may be possible, but sometimes the pump is simply beyond a practical rebuild. Dunham Well Drilling has a full-line machine shop for in-house pump and turbine rebuilds, which helps us diagnose whether repair makes sense.

Loss of prime on shallow or jet pump systems

If you have a shallow well or jet pump, the system can hum but not pump when it loses prime. That means air has entered the line, or water has dropped below the point where the pump can draw it properly.

Typical causes include:

• A leak in the suction line
• A foot valve that is not holding
• Low water level in the well
• A clogged intake or strainer

For properties that rely on a shallow irrigation well, this can show up after dry weather or after system work. If the well itself is the issue, we can evaluate whether a new well or a different setup is the better long-term fix. Learn more about our Water Well Drilling and Shallow (2-Inch) Irrigation Wells services.

Pressure tank, switch, and pump problems often overlap

Many homeowners hear the humming at the same time the pressure drops or the system cycles strangely. That is because the pump, pressure tank, and pressure switch work together.

A bad pressure switch may fail to start the pump correctly. A waterlogged or failing pressure tank can cause rapid cycling and strain the system. And if the pump is already weak, those added stresses can be enough to keep it from pumping at all.

We handle pump repair and installation, including pressure tanks, residential pumps, irrigation pumps, turbine pumps, industrial pumps, and centrifugal pumps. We also carry Goulds, Sta-Rite, Grundfos, and Schaefer pumps and parts, new and used. See our Pump Repair & Installation page for more on the systems we service.

When the problem is lightning damage

In Polk County and across Central Florida, lightning is a real cause of pump and control failure. A strike can damage the motor, pressure switch, controls, or irrigation electrical components.

If your pump started humming after a storm, that is a strong clue. We offer Lightning Damage Repair and can work directly with your insurance company on the claim.

Water quality can contribute to pump trouble too

If your water has sand, iron, or sulfur issues, those conditions can shorten pump life and contribute to internal wear. A humming pump may be the symptom, but the underlying problem can be poor water quality or buildup in the system.

Dunham also provides Water Filtration & Treatment for hard, smelly, or staining well water. We can test the water on-site to see what is actually in it and recommend a system that fits the problem, whether that is a softener, chlorination, iron removal, iron-sequestering, or hydrogen sulfide treatment.

What to do right away

If your well pump is humming but not pumping, take these steps:

• Turn the pump off at the breaker or switch
• Do not keep trying to restart it over and over
• Check whether the issue started after a storm or power loss
• Note whether the problem is on a drinking water well, irrigation system, or both
• Call a licensed well contractor for diagnosis

Do not try to work inside the electrical service, pressure tank, or well system yourself. That can make the problem worse and create a safety hazard.

Call Dunham Well Drilling for pump diagnosis in Central Florida

If your well pump is humming but not pumping, call Dunham Well Drilling at (863) 965-2881 for prompt help from a family-owned shop that has served Polk County since 1950. We have a 24/7 answering service and return calls within 48 hours, and our full machine shop lets us rebuild many pumps and turbines in-house instead of guessing at the fix.