Well Pump Troubleshooting + Service
Why this matters
A failed well pump = no water in the house. Rural customer panics; calls go in priority order. The well-pump-competent plumber gets the call + bills typical residential service / replacement. Without that capability, the work goes to the well driller (slower, more expensive) + you lose the customer relationship. Well pumps are deceptively simple - pump, pressure tank, pressure switch, controls - but the diagnostic logic separates the pro who fixes it in 1 hour from the tech who replaces of parts unnecessarily.
Well pump types
- Submersible (90%+ of new): sealed motor + impellers in well casing on PEX/poly + electrical wire; 1/2 - 1 HP residential up to 5 HP; 240V single-phase; pull whole pump to service.
- Shallow-well jet (suction well < 25 ft): surface-mounted, single suction pipe, limited by atmospheric pressure; fails from lost prime + venturi eductor wear.
- Deep-well jet (older 25 - 200 ft): surface pump with two pipes; eductor at bottom creates suction; largely replaced by submersibles.
- Hand pump: emergency / off-grid only.
System components
Pump moves water from aquifer. Pressure tank (20 - 80 gal residential bladder) stores pressurized water; pre-charge air = 2 PSI below cut-in; failed bladder = pump short-cycles. Pressure switch cuts in/out (30/50 PSI common, 40/60 for higher demand); adjustable via nut. Check valve holds water in pipe when pump off; submersibles built-in; failed = back-drain to well = short cycles. Pressure gauge on tank. Control box (jet pumps + 3-wire submersibles): capacitor start; failed capacitor = won't start.
Common service calls + diagnostics
"No water at house"
Quick check sequence:
- Verify pump's breaker on (240V double-pole)
- Verify pressure switch trip - clean contacts if dirty
- Manually push pressure switch lever - does pump start?
- Pressure gauge reading: 0 = pump not running; high = check valve failed open in line
- Listen at well head - pump should hum
If pump won't start:
- Breaker tripped → check pump amperage on restart
- Pressure switch failed → bypass with jumper temporarily
- Control box capacitor blown → replace
- Pump motor seized → pull pump
If pump runs but no water:
- Lost prime (jet pump) → re-prime via priming port
- Discharge pipe broken → look for leak in basement / line
- Suction lift exceeded (jet pump shallow) → drop pump or convert to submersible
- Pump impellers worn → pull + inspect
- Air-lock in pipe → bleed at highest point
"Pump short-cycles"
Pump on/off every 30 - 90 sec. Waterlogged pressure tank (90% of cases) - bladder failed; test by shutting pump + opening faucet (tank empties immediately = bladder fail); fix is tank replacement. Switch differential too tight - adjust differential nut. Failed check valve - water back-drains, pump restarts immediately. Pre-charge wrong - tank should be 2 PSI below cut-in (28 PSI for 30/50 switch); drain, measure at Schrader, recharge.
"Pump runs constantly"
Major leak somewhere (visible plumbing, running toilet, broken irrigation, burst pipe in crawlspace), failed pressure switch stuck closed. Walk system at silent moments listening for leaks.
"Low water pressure"
Pressure switch set too low (raise cut-out), pump pulling air (lost prime, dropping water table), worn impellers, calcified pipe or partially-closed valve, clogged house sediment filter.
"Sandy / silty water"
Drop pipe broken (pump pulling bottom sediment), water table dropped near sediment, failed well screen, exhausted filter media. Solution: pull pump + raise pitless adapter OR drill deeper.
"Smelly water (rotten egg)"
Hydrogen sulfide from anaerobic bacteria in well OR sulfur-reducing bacteria in water heater. Solution: chlorinate well, replace anode rod (aluminum/zinc), install whole-house activated carbon. Persistent cases: aeration system + treatment.
Diagnostic tools
- Multimeter (240V verification, motor resistance test)
- Pressure gauge (check tank + line pressure)
- Tire gauge (check tank pre-charge at Schrader)
- Pipe wrenches + pump pullers
- Clamp-on ammeter (verify motor running amps within spec)
Pulling a submersible pump
When pump must be replaced:
- Shut off breaker; lock out
- Disconnect electrical at well head
- Disconnect discharge pipe at pitless adapter (or pull through casing top)
- Use pump puller OR rented tripod for 30+ ft depth
- Pull pipe + pump together; coil pipe carefully
- Replace pump with new (or rebuild if worth doing)
- Inspect/replace torque arrestor, check valve, splice + heat shrink
- Reinstall lowering pump to original depth
- Restore power; verify proper rotation + flow
Service contract opportunity
Annual well system service:
- Pressure tank pre-charge check
- Pressure switch operation + contact cleaning
- Pump amperage measurement
- Water sample to lab (basic chemistry)
- Filter cartridge replacement (if installed)
- Visual inspection of wellhead + access
Customer with rural well + dependence has high willingness to pay for prevention vs failure.
The single most-overlooked diagnostic step on a "pump short-cycle" call is checking the PRESSURE TANK PRE-CHARGE with the system off. Drain tank to 0 PSI, then test with a tire gauge at the Schrader valve. 60% of "failed pump" complaints are actually a waterlogged bladder tank causing the pump to short-cycle until the motor overheats + trips. Replacing the tank fixes the problem; replacing the pump doesn't + customer comes back angry. The 5-minute pre-charge test before pulling any pump is the difference between a competent diagnostic + an expensive misdiagnosis.
References
- Goulds Pumps Service Manual (industry reference)
- Franklin Electric Submersible Pump Service Guide
- Water Systems Council (WSC) installation standards
- State well-driller licensing (varies)
- Manuall internal: Well Water Systems, Annual Plumbing Inspection