How to Diagnose Submersible Pump Air-Lock and Priming Issues

Submersible well pumps are designed to operate underwater and typically don’t require priming in the same way surface jet pumps do. Yet, homeowners often experience symptoms that feel like priming loss—no water, sputtering faucets, and pressure that won’t build. In many cases, the root cause is an air-lock in the drop pipe, a partially drained line, or a mechanical or electrical fault that mimics low-water conditions. This guide walks you through a practical, safety-first, DIY well inspection workflow to diagnose air-lock and priming-like issues before calling a pro. We’ll weave in essential well pump troubleshooting steps, from using a well pressure gauge to running a pressure switch test, and when to verify electrical continuity with a multimeter.

Key symptoms that suggest air-lock or priming-like issues:

Faucets sputter with intermittent bursts of air and water The well pressure gauge stalls at a low PSI and won’t recover Long recovery time after water use or complete loss of pressure Pump appears to run continuously or short-cycle

Important safety note: If you are not comfortable working around electricity or pressurized plumbing, stop and call a licensed well contractor. Always de-energize the circuit before opening any wiring compartment.

1) Start with the basics: power and protection

Check the breaker panel: Is the breaker tripped for the well circuit? Reset once only; if it trips again, stop and investigate for shorts, failed components, or motor issues. Verify the pump control box (if your pump uses one). Many 3-wire submersible pumps rely on a control box for start/run capacitors and relays. Burn marks, bulged capacitors, or a hot electrical odor indicate failure. Perform a well pump reset if your system includes a protective device (overload or pump saver). Some boxes auto-reset after cooling; others have a manual reset. Use a multimeter to confirm voltage at the pressure switch and control box. With the power off, inspect for loose lugs, corroded terminals, or brittle insulation.

2) Read the well pressure gauge to guide your next move Your well pressure gauge tells a story:

If pressure rests at zero and never rises when the pump should be on, suspect no power to the pump, a failed pump/motor, a broken or air-bound drop pipe, or an empty well. If pressure rises slightly (e.g., to 10–20 PSI) and stalls, consider an air-lock, a major leak in the system, or a failing impeller. If pressure quickly cycles between cut-in and cut-out, look for a waterlogged pressure tank or a small leak.

3) Confirm if the pressure switch is calling for water

Observe the contacts: With faucets open and low pressure at the gauge, the pressure switch should be closed (contacts snapped together). If not, the switch may be stuck, misadjusted, or the sensing tube clogged. Pressure switch test: De-energize power. Remove the cover and inspect for pitting or insects. Restore power and carefully observe whether the contacts close at cut-in (e.g., 30 PSI). If contacts don’t close despite low pressure, replace the switch and verify the nipple/tube is not clogged with sediment. If contacts close but the pump doesn’t run, you likely have a power delivery or motor issue downstream.

4) Air-lock and “priming” behavior in submersible systems While submersibles self-prime, the discharge plumbing can trap air, especially after maintenance, partial draining, or severe leaks. Air-lock is more likely:

After the system is opened (filter changes, plumbing work) With high points in the line where air can collect When check valves fail, allowing water to drain back and introduce air

How to clear a suspected air-lock:

Bleed air at the highest accessible fixture. Open an upstairs faucet fully while running water at a lower fixture. If pressure is low, crack fittings at an upstairs hose bib or boiler drain (carefully) to vent air, then re-tighten. Cycle demand and recover: Open a faucet slightly to maintain flow while the pump tries to build pressure. Watch the well pressure gauge; if you see incremental increases with spitting air at fixtures, you’re clearing the line. Inspect and orient check valves. Most systems use a single check valve integral to the pump. Additional topside checks can cause nuisance air-locks. If an added check valve is installed near the tank, consider removing it after consulting a pro.

5) Rule out tank and switch problems that mimic air issues

Check the pressure tank’s air charge with the power off and system drained to 0 PSI. Use a tire gauge on the Schrader valve. The precharge should be 2 PSI below the switch’s cut-in (e.g., 28 PSI for a 30/50 switch). A wrong precharge causes short-cycling or poor pressure. If water spurts from the tank’s Schrader valve, the bladder has failed. Replace the tank; otherwise, the pump will short-cycle, creating erratic pressure that resembles air-lock.

6) Electrical checks: continuity and motor health If airflow bleeding doesn’t restore pressure and the breaker hasn’t tripped again:

With power off, check electrical continuity of leads at the wellhead or control box using a multimeter. Compare readings to the pump manufacturer’s specs. An open winding or ground fault points to a failed motor. Start components: In a pump control box, test capacitors with a meter that reads microfarads. Replace swollen or out-of-spec capacitors. Faulty start components can prevent the pump from starting, which can look like a no-prime issue. Insulation resistance (megohm) testing is best left to pros, but if available, it’s the gold standard to identify motor-to-ground faults.

7) Mechanical and plumbing checks

Listen for flow and vibration in the drop pipe while the pressure switch calls for water. Silence may indicate a non-running pump or a broken pipe below grade. Inspect for leaks between the well and the pressure tank, including pitless adapter connections and buried lines. A major leak introduces air and caps pressure at a low PSI. Sediment and clogged filters can choke flow. Temporarily bypass post-tank filters and softeners; if pressure normalizes, service the filters.

8) When to suspect the aquifer or well recovery Low producing wells can draw down, allowing air entrainment at the pump intake or the pressure to collapse:

Observe behavior after long rest. If pressure recovers only after hours and then drops rapidly under use, you may be outrunning the well. A pump saver may trip under these conditions. If the breaker isn’t tripped but water stops, your protection device may be doing its job. This is where well pump reset behavior and logs on the pump control box can help.

9) Step-by-step DIY well inspection workflow

Verify power: breaker tripped? Reset once. Confirm voltage at the pressure switch and control box with a multimeter. Observe the pressure switch test: contacts should close at cut-in. Clean or replace if stuck; confirm clear sensing line. Read the well pressure gauge under demand. Note stall points and cycling. Bleed air at high fixtures to clear air-lock; avoid extra topside check valves. Validate pressure tank precharge and bladder integrity. Bypass filters briefly to rule out restriction. Check electrical continuity and start components in the pump control box if equipped. If still unresolved, consult a professional for submersible pump testing, megger tests, and potential pull of the pump.

10) Preventing future air-lock and false priming issues

Limit additional check valves beyond the pump’s built-in valve. After any plumbing service, deliberately bleed air at high fixtures before normal use. Service or replace clogged filters regularly. Keep an eye on the well pressure gauge trends and log any abnormal pressure plateaus. Schedule periodic well pump troubleshooting to test controls, the pressure switch, and electrical integrity.

Frequently Asked Questions

Q1: How can I tell if my issue is air-lock versus a bad pump? A1: Air-lock often comes with sputtering faucets and gradual pressure climbs as air bleeds out. A bad pump typically yields no pressure increase at all, even with the pressure switch calling. Use the well pressure gauge to observe behavior and perform a pressure switch test. If the breaker isn’t tripped and you measure correct voltage with a multimeter but see no pressure rise, test electrical continuity or components in the pump control box and consider professional submersible pump testing.

Q2: Do submersible pumps need priming? A2: No, submersible pumps are self-priming by design because they operate underwater. However, the discharge plumbing can trap air after maintenance or leaks, producing symptoms that look like priming loss. Clearing trapped air and verifying check valve configuration usually resolves it.

Q3: Why does my breaker keep tripping when the pump runs? A3: Repeated trips suggest electrical faults (shorted wiring, failed motor windings), seized pump, or failing start components. Reset only once. Then perform voltage checks, inspect the pump control box, and test electrical continuity. If trips persist, call a pro.

Q4: My pressure tank seems fine—could filters be the problem? A4: Yes. Severely clogged filters restrict flow and can make pressure build slowly or stall. Temporarily bypass them during diagnosis. If pressure normalizes, service or replace the filters.

Q5: When should I stop DIY and call a professional? A5: If you’re uncomfortable with electrical work, if the breaker trips repeatedly, if continuity or megger testing is needed, or if clearing air-lock doesn’t restore normal operation. A licensed contractor can perform advanced diagnostics, including submersible pump testing and a full DIY well inspection review.