How To Tell If My Well Pump Is Bad: Diagnostic & Testing Guide

A failing well pump typically manifests through irregular water pressure, continuous cycling of the pressure switch, strange mechanical noises, or a complete loss of water delivery. Diagnosing the issue requires a systematic evaluation of electrical parameters, pressure tank integrity, and motor performance using a digital multimeter and pressure gauge.

Preparing for Your Well System Inspection

• Before you begin troubleshooting your submersible or jet pump, gather the proper diagnostic tools and safety equipment. Well systems handle high-voltage electricity and pressurized water, making safety protocols mandatory.
• Essential gear, tools, and materials: Digital multimeter capable of measuring AC/DC voltage and resistance in ohms, 0-100 PSI water pressure gauge with a hose bib adapter, insulated screwdrivers, tongue-and-groove pliers, work gloves, and safety glasses.
• Mandatory prerequisite knowledge and standards: Familiarity with National Electrical Code (NEC) standards for pump circuits, basic understanding of hydraulic pressure cycles (typically 30/50 or 40/60 PSI), and awareness of confined space risks around wellheads.
• Estimated budget and duration benchmarks: Diagnostic testing takes 45 to 90 minutes. If professional replacement is required, a standard pump replacement costs between 1,500 and 3,500 dollars depending on well depth and pump horsepower.

Step-by-Step Well Pump Diagnostic Workflow

Step 1: Inspect the Pressure Tank and Pressure Switch

• Locate your pressure tank and pressure switch, usually situated near the pressure tank in your basement, utility room, or wellhouse. Remove the plastic cover of the pressure switch and inspect the electrical contacts for pitting, burning, or insect nesting.
• Check the air pre-charge inside the pressure tank when the system is fully drained of water. Turn off the power to the pump at the main circuit breaker, open a nearby faucet until all water drains out, and check the Schrader valve on top of the tank using a standard tire pressure gauge.
• The tank air pressure should read exactly 2 PSI below the cut-in pressure of your switch (e.g., 28 PSI for a 30/50 switch). If water sprays out of the Schrader valve, the internal bladder is ruptured, and the tank must be replaced immediately.

Step 2: Test Electrical Power at the Pressure Switch

• Restore power to the well pump circuit breaker and carefully measure the incoming voltage across the line terminals of the pressure switch using your digital multimeter set to AC volts. You should read approximately 230 volts (or 115 volts for shallower jet pump setups).
• Manually close the pressure switch contacts using an insulated tool while observing the load side terminals, exercising extreme caution around live electrical components. If the switch shows proper incoming voltage but fails to send power to the pump motor when closed, the pressure switch is defective.
• If the switch contacts are closed, power is successfully transmitted down the drop cable to the pump, but no water is pumped and the motor remains silent, the internal thermal overload switch inside the motor may have tripped, or the motor windings have burned out.

Step 3: Measure Motor Amperage and Resistance at the Control Box

• For 3-wire submersible pumps, open the external control box and test the start capacitor, run capacitor, and relay switch for signs of melting, bulging, or a strong acrid odor. Use your multimeter to check microfarad ratings against the manufacturer specifications printed on the capacitor label.
• Measure the running amperage draw of the pump motor using a digital clamp meter placed around the black wire connected to the pressure switch or control box. Compare this measured amperage against the Service Factor Amps (SFA) rating stamped on the pump motor data plate.
• If the running amperage significantly exceeds the SFA rating, the pump is experiencing a locked rotor condition, mechanical binding from sediment, or failing bearings. If the meter shows infinite resistance (OL) across the motor winding terminals, you are dealing with a dead short or a severed drop cable.

Common Well Pump Failures and Field Fixes

• Root Cause: The well pump cycles on and off rapidly (rapid cycling) every time a faucet is trickled, eventually burning out the motor. Actionable Fix: Drain the pressure tank completely to reset the air-to-water ratio, or replace the waterlogged pressure tank and check for hidden plumbing leaks.
• Root Cause: The pump runs continuously without shutting off, failing to reach the cut-out pressure threshold. Actionable Fix: Check for a broken drop pipe inside the well casing, a stuck check valve letting water drain backward, or a severely lowered water table starving the pump intake.
• Root Cause: Water spurts from faucets, delivering a mixture of air and water alongside heavy sputtering. Actionable Fix: Inspect the suction line or foot valve for air leaks, lower the pump depth in the well if the water table has dropped, or replace a worn pump impeller assembly.
• Root Cause: The circuit breaker trips instantly every time the well pump attempts to start up. Actionable Fix: Inspect the underground well wire for rodent damage, test the control box capacitors for short circuits, or pull the pump to inspect for motor winding failure.

Frequently Asked Questions

How long does a standard residential well pump last?

Most submersible well pumps last between 8 and 15 years, depending heavily on water quality, installation depth, and daily operational cycle frequency. Systems operating in high-mineral or sandy water tables experience accelerated mechanical wear on impellers and bearings, often requiring replacement sooner.

Can a bad pressure switch mimic a failing well pump?

Yes, a faulty pressure switch is one of the most common culprits behind well system failure and often mimics a bad pump motor. If salt corrosion, sand buildup, or burned contacts prevent the switch from transmitting electricity, the pump will not run even if the motor itself is in perfect condition.

What are the signs of a failing check valve?

When a check valve fails, water drains backward through the pump and back down into the well when the motor shuts off. This causes the pressure tank to lose pressure rapidly, forcing the pump to cycle on and off frequently even when no household water is being consumed.

Should I pull the well pump myself or hire a professional?

Pulling a submersible pump from a shallow well (under 100 feet) can be done with multiple people and a lifting tripod, but deep wells require specialized truck-mounted pulling rigs and safety winches. Attempting to pull a deep well pump without professional equipment risks dropping the entire pump and drop pipe assembly down the casing.

Inspect your well system components today and test your pressure switch to accurately identify failing parts before complete water loss occurs.