How To Tell If Your Well Water Pump Is Bad
A failing well pump typically manifests through fluctuating water pressure, continuous cycling, strange mechanical noises, or a complete loss of water delivery. Diagnosing the issue requires isolating electrical supply issues, pressure switch malfunctions, and mechanical wear inside the submersible or jet pump assembly.
Pre-Operation & Equipment Safety Checklist
Troubleshooting a domestic water system requires a methodical approach to isolate whether the root cause is electrical, hydraulic, or mechanical. Before opening control boxes or checking the pressure tank, assemble the correct instrumentation and observe safety protocols to prevent electrical shock or system contamination.
- Essential Gear, Tools, and Materials:
- Digital multimeter capable of measuring AC/DC voltage and continuity (ohms)
- Insulated screwdrivers and channel-lock pliers
- Non-contact voltage tester for safety verification
- Flashlight or headlamp
- Pipe wrenches for pressure switch and union checks
- Mandatory Prerequisite Knowledge and Standards:
- Familiarity with National Electrical Code (NEC) standards regarding pump circuits (typically 230V or 115V)
- Understanding of potable water sanitation protocols to avoid wellhead contamination
- Basic knowledge of well hydraulics, including cut-in and cut-out pressure settings (e.g., 30/50 or 40/60 PSI)
- Estimated Budget and Duration Benchmarks:
- Initial diagnostic troubleshooting: 45 to 90 minutes
- Professional replacement cost range: $800 to $2,500 depending on pump depth and horsepower (1/2 HP to 2 HP)
Step-by-Step Diagnostic Procedure
Step 1: Inspect the Pressure Switch and Control Box
Locate your pressure switch, typically mounted on a nipple near the pressure tank. Remove the plastic cover to visually inspect the contact points for pitting, burning, or insect infestation. Use a non-contact voltage tester to confirm power status, then use a thin piece of non-conductive cardstock to gently clean debris from the metal contacts if they appear dirty.
Warning: Mains voltage is actively present inside the pressure switch cover. Always shut off the dedicated circuit breaker at the main electrical panel before performing continuity tests or tightening terminal screws.
Step 2: Test Electrical Continuity and Amp Draw
Using your digital multimeter set to the appropriate voltage scale, test the incoming power supply at the pressure switch terminals while the pump is calling for water. Next, measure the amperage draw on the hot wires leading to the pump and compare the measured value against the Service Factor Amps (SFA) listed on the motor's technical specification plate. An amperage draw significantly exceeding the SFA indicates a locked rotor, winding short, or failing motor bearings.
Pro-Tip: If the pressure switch contacts are closed, power is flowing to the pump, but the motor fails to hum or run, check the control box relay and start/run capacitors for bulging, leaking oil, or internal short circuits.
Step 3: Evaluate the Pressure Tank and Water-Logged Bladder
Examine the pressure tank by checking the Schrader valve located on top of the vessel using a standard tire pressure gauge. If water sprays out of the Schrader valve, the internal bladder or diaphragm has ruptured, causing the pump to short-cycle rapidly. If the tank feels entirely heavy and full of water with no air charge, manually drain the system and repressurize the tank to 2 PSI below the pump cut-in pressure (e.g., set to 28 PSI for a 30/50 switch setting).
Step 4: Perform a Well Yield and Drawdown Test
If the pump motor runs continuously without shutting off but delivers low or sputtering water pressure, isolate the system at the main supply line just after the pressure tank. Open a downstream spigot and monitor the pressure gauge; if pressure drops rapidly to zero while the pump runs endlessly, the well may be experiencing low yield, a severed drop pipe, or worn pump impellers that can no longer generate hydraulic lift.
How To Tell If Your House Water Pump Is Bad | Storables
Well Pump Diagnostic Parameter Matrix
| Symptom | Primary Component Affected | Diagnostic Test Method | Target Standard / Normal Threshold |
|---|---|---|---|
| Continuous Cycling | Pressure Tank / Switch | Check Schrader valve for water; measure switch cut-in/cut-out | Air charge should equal Cut-In minus 2 PSI (e.g., 28 PSI for 30/50) |
| Complete Power Loss | Breaker / Control Box | Test continuity across pressure switch terminals with multimeter | 0 ohms when closed; infinite ohms when open |
| High Amperage Draw | Pump Motor Windings | Measure running amps with a clamp meter against SFA rating | Must not exceed motor's Service Factor Amps (SFA) |
| Sputtering Faucets | Drop Pipe / Check Valve | Isolate supply and monitor pressure drop during active pumping | System should hold steady pressure without rapid bleed-back |
Common Site Failures and Field Fixes
Failure Scenario: Rapid Short-Cycling (Pump turns on and off every few seconds when a faucet is open)
- Root Cause: Water-logged pressure tank due to a failed internal bladder or a complete loss of compressed air pre-charge.
- Actionable Fix: Turn off power to the pump, drain all water from the system, check the air pressure via the Schrader valve, and repressurize or replace the pressure tank if the bladder is ruptured.
Failure Scenario: Motor Hums Loudly but Fails to Start
- Root Cause: Seized pump wet end, sand-locked impellers, or a failed start capacitor inside the external control box.
- Actionable Fix: Replace the start/run capacitor. If the motor still hums and trips the thermal overload breaker, pull the pump assembly to inspect the mechanical pump shaft and impellers for debris.
Failure Scenario: Water Surges with Air Pockets and Sputters Consistently
- Root Cause: A pinhole leak in the drop pipe inside the well casing, a failing foot valve, or the water table dropping below the pump intake level.
- Actionable Fix: Inspect surface check valves and fittings for air leaks. If fittings are secure, lower the pump assembly further into the well column or inspect the drop pipe for structural compromise.
Frequently Asked Questions
How long does a typical well water pump last?
A standard submersible well pump generally lasts between 10 to 15 years, while jet pumps installed above ground typically last 8 to 10 years. Lifespan is heavily influenced by water chemistry, sand content, and the frequency of pump motor cycling.
Can a bad pressure switch mimic a bad well pump?
Yes, a malfunctioning pressure switch with burned contacts, insect nests, or clogged internal ports can prevent electrical power from reaching the pump entirely. Always test the electrical switch before condemning the downhole pump motor.
What causes a well pump to run constantly without stopping?
A continuously running pump usually indicates a severed drop pipe, a stuck-open pressure switch, severely worn pump impellers that cannot build pressure, or a depleted well yield where the pump is running dry.
Is it safe to run a well pump when it is sputtering air?
No, running a well pump dry or with heavy air entrainment causes rapid overheating of the motor windings and can melt plastic impellers within minutes. Shut off the system immediately until the water source and plumbing integrity are verified.
Protect your home water supply by scheduling a professional diagnostic assessment or replacing failing components before total system failure occurs.
