Well Pump Service Call
Purpose
Almost every private well complaint arrives in one of three sentences: no water, water that surges, or a pump that clicks on and off constantly. Two faults produce all three, in different equipment: the pump and its supply, or the pressure tank, a consumable that fails silently and costs a fraction of a pump to put right. The reading that separates them is the tank precharge, measured with zero water pressure on the tank, and it takes ten minutes. A shop that skips it sells pumps that did not need replacing, then sells the tank six months later when the new pump short cycles too.
Scope
Covers diagnostic and corrective service on private well systems, residential and light commercial: submersible and jet pumps, bladder and diaphragm tanks, pressure switches, check valves and low-pressure cutoffs, from the well head to the first shutoff.
Does not cover pulling a submersible pump or drop pipe, which needs a hoist and a rigging plan this SOP will not compress into a step, or well drilling, casing repair and yield testing, which belong to a licensed well contractor. Does not cover water quality complaints, which have their own SOP: this one tells you the pump is delivering, that one owns whether what it delivers is acceptable.
Roles and responsibilities
| Role | What they own | The handoff |
|---|---|---|
| Dispatcher | The complaint in the customer's words, whether there is water now, whether anyone reset a breaker | Puts the reset history on the ticket; a breaker reset three times is a different call from one that never tripped |
| Technician | Isolation and proving dead, the as-found readings, the precharge, the verdict | Returns the as-found cut-in and cut-out, the precharge and the drawdown comparison; a verdict without those three is not a verdict |
| Lead or owner | Any recommendation to pull the pump, and any yield conversation | Owns the call where the answer is "this needs a well contractor", since that quote turns on yield a plumber cannot measure |
Procedure
Find the disconnect before you find the problem, and treat every cover as live. Locate the breaker or disconnect serving the pump and confirm you can operate it. Acceptance: the disconnect identified, labeled if it was not, and accessible. Wrong looks like opening a pressure switch cover to "just look" while energized. Stop rule: if you cannot positively identify this pump's disconnect, open no electrical enclosure until you have. Hazard: a residential submersible circuit is commonly 240 V and the switch cover conceals line-voltage terminals a hand's width from a grounded metal tank, often over a wet floor; nothing opens before step 3.
Watch a full cycle hands off, and take the numbers from the gauge, not the label. Open a fixture, let the system run, and record the pressures the pump starts and stops at and how long it runs. Acceptance: an observed cut-in, an observed cut-out, and a timed run in seconds. Wrong looks like reading 40/60 off the switch label when a previous tech may have turned the range nut. Stop rule: a pump that does not start, or runs and never builds pressure, is an electrical or pump fault; leave the tank alone and go to steps 3 and 6. Hazard: no covers come off and no hands go near the switch here, and observe from somewhere you are not standing in water.
De-energize, prove dead, and discharge stored energy before any enclosure is opened. Open the breaker or pull the disconnect, verify absence of voltage at the pressure switch terminals with a tester proved live immediately before and after, and on a three-wire submersible discharge the control box start capacitor per its manufacturer's instruction. Acceptance: no voltage on any conductor you will touch, on a proved instrument, and the capacitor at zero before a terminal is handled. Wrong looks like trusting a labeled breaker on a panel rearranged over thirty years. Stop rule: voltage after the disconnect is open means another feed, and work stops until it is found; without the discharge instruction for that box, do not open it. Hazard: electrical utilization work, which 29 CFR 1910.147 excludes at (a)(1)(ii)(C), so the controlling practice is 29 CFR 1910.333(b)(2), 29 CFR 1926.417 in construction, with live-dead-live at NFPA 70E-2021, 120.5. A charged capacitor is stored energy an open breaker does nothing about.
Drain the tank fully, then measure the precharge with zero water pressure on it. With the pump de-energized, open the lowest drain or a hose bib, let the tank empty, then depress the schrader. Acceptance: the system gauge at zero with the drain stopped rather than trickling, then a precharge in psi with air, not water, coming out. Wrong looks like a tire gauge on the schrader while the tank still holds 40 psi of water, which reads the system, not the precharge, and always looks correct. Stop rule: a gauge that will not fall to zero means a check valve is holding pressure on the tank side, so isolate further before reading, since a precharge read against residual water is worthless; water at the air valve is a ruptured bladder and a tank replacement, recorded before any pump work; a galvanized air-over-water tank has no schrader, so it gets an air volume control and water level check instead. Hazard: the tank is a pressure vessel at full system pressure, so relieve through a drain rather than by cracking a fitting, and never depress the air valve on a tank you have not fully drained - it sprays water at pressure into your face.
Set the precharge to the rule, then prove the drawdown against the published table. Charge the empty tank to 2 psi below the cut-in observed in step 2, then restore power, build to cut-out, de-energize again, and draw water into a measured container until the gauge falls to cut-in. Acceptance: the chuck gauge reads cut-in minus 2 psi and holds a minute after the chuck is removed, and measured drawdown lands within the published figure for that tank model at that switch setting. Wrong looks like charging to cut-out, or to whatever the last tech wrote on the tank, which starves the drawdown and produces the short cycling the customer called about, or judging drawdown by how long a shower lasts. Stop rule: a tank that will not hold that charge for a minute has a leaking schrader core or bladder, so replace the core and re-test before condemning the tank; drawdown materially below the published figure on a correctly precharged tank means a partially collapsed bladder or a tank undersized for the setting, a tank finding that goes on the record before any pump is discussed. Hazard: a compressor drives a small tank past its stamped maximum working pressure quickly, so charge in short bursts against a gauge, and restoring power makes the pump circuit live again, so covers go back on before the breaker is closed, not after.
Check supply voltage under load and running amperage against the nameplate. With the pump running, read voltage at the pressure switch line terminals and clamp running current on the motor leads. Acceptance: voltage within the motor manufacturer's stated tolerance under load, and running amperage at or below nameplate. Wrong looks like reading voltage with the pump off, which looks fine on a circuit that sags badly under starting load. Stop rule: voltage outside tolerance under load is a supply fault, fixed before the pump is condemned, because a motor run low draws higher current and causes the overload trips blamed on the pump. Hazard: a live reading at an open enclosure is energized work, so use the right category of instrument and leads, keep one hand out of the enclosure, and never take it standing in water.
Inspect the switch contacts, the low-pressure cutoff and the check valve before you close up. Acceptance: contacts clean and closing squarely, the low-pressure cutoff (where fitted) resetting as designed, and the check valve holding pressure over a timed hold rather than bleeding back. Wrong looks like replacing a switch on pitted contacts without asking why they pitted, when short cycling from a dead tank burned them. Stop rule: pitted contacts on a short-cycling system are a symptom, so the switch goes in as part of the tank fix rather than as the fix; replacing only the switch returns the call within weeks. Hazard: the switch is opened with the circuit proved dead per step 3 and the tank relieved per step 4, because the switch tailpiece is a water joint on a pressurized system.
Verify against the original complaint and time a cycle before you leave. Acceptance: the stated symptom reproduced and gone, a timed cycle of at least about a minute of run per start under a normal continuous draw, and pressure holding at cut-out with all fixtures closed. Wrong looks like leaving because the gauge looks right. Stop rule: a timed cycle still short means the diagnosis is not complete, whatever parts were changed; go back to step 4. Hazard: leave the customer the disconnect location and tell them to switch the pump off rather than repeatedly reset a tripping breaker, because repeated resets are how a motor fails hard.
The record this produces
Nine fields filed by the office against the address, not just the invoice: observed cut-in and cut-out from step 2; timed run per cycle before and after; precharge as found; precharge as set; tank make, model and size; measured drawdown against the published figure; running voltage under load; running amperage against nameplate; and the verdict naming which component was at fault.
They land on the property record so they can be compared: the next tech reads last visit's precharge against this one (a tank that has lost charge twice in two years is at the end of its life, not a mystery), the office reads the verdict for warranty questions, and the lead reads amperage drifting toward nameplate across visits as the earliest warning of a failing motor.
One worked pass, including a failure
Rural house, submersible pump, three-wire with a control box, bladder tank in the basement. Complaint: "the pump clicks on and off constantly when we shower."
Step 2, hands off: cut-in 40 psi, cut-out 60 psi, matching the switch label; with a shower running the pump runs 9 seconds per start. Against the rule of about a minute per start that is severe short cycling, written down before any cover moves. Step 3: the labeled breaker is opened and proved dead at the switch terminals, tester checked on a live receptacle before and after, and the control box capacitor discharged before any lead is pulled.
Step 4: the tank drains until the gauge sits at zero. The schrader gives air, not water, and reads 12 psi against a target of cut-in minus 2, or 38 psi. Twelve is not a bladder failure, it is a tank bled down over years, and a tech who stopped here would have charged it and left.
Step 5 half-fails. The empty tank takes 38 psi and holds the one-minute check, but measured drawdown comes in at roughly a third of the published figure for that tank at 40/60, and at a third of the drawdown the pump starts about three times as often for the same volume drawn, which is the complaint. Stop rule taken: the tank is recorded as failed on drawdown despite a correct precharge, pointing at a partially collapsed bladder. No pump work is proposed this visit.
Step 6 runs anyway, because a verdict without it is not a verdict: voltage under load sits inside the motor's tolerance and running current is below nameplate, ruling supply and motor out. Step 7 finds the contacts pitted, a symptom of the short cycling, so the switch goes in as part of the tank job rather than sold as the fix. Step 8, after tank and switch: 40/60, precharge 38 psi, drawdown matching the published figure, timed cycle 1 minute 20 seconds per start. Complaint reproduced and gone.
References
- 29 CFR 1910.333(b)(2) for electrical safe work practices, with the 1910.147(a)(1)(ii)(C) carve-out routing electrical utilization work there, 29 CFR 1926.417 as the construction counterpart, and NFPA 70E-2021, 120.5 for the live-dead-live sequence in step 3.
- Pressure tank, pump and control box manufacturer literature: the published drawdown table at each switch setting, the stamped maximum working pressure, the precharge rule, capacitor discharge, nameplate amperage and voltage tolerance.
- See related: the Plumbing water quality complaint visit SOP, which owns what the well delivers once this one confirms it delivers.