Air Lock in Well Pump: How to Fix & Prevent

An air lock is one of the most common—and frustrating—problems well owners face. Your pump runs, the motor hums, but no water comes out of the faucet. Understanding what causes air locks and how to clear them can save you from an emergency service call and get your water flowing again in minutes.

In this comprehensive guide, we'll cover everything you need to know about air locks in well pumps, including how to diagnose the problem, step-by-step clearing instructions for different pump types, and prevention strategies that keep your system running smoothly.

What Is an Air Lock in a Well Pump?

An air lock occurs when air becomes trapped in your well pump or the pipes leading to it, preventing water from flowing. Think of it like a bubble in a straw—the air creates a barrier that the pump can't push past, even though the motor is running perfectly fine.

Unlike a mechanical failure where something is broken, an air lock is a hydraulic problem. The pump is working, but it's trying to move air instead of water. Because air compresses differently than water, the pump can't build the pressure needed to push water through your system.

How Air Locks Affect Different Pump Types

Jet Pumps (Above-Ground): These are most susceptible to air locks. Jet pumps must maintain a column of water from the well to the pump housing. If air enters this column, the pump loses its prime and can't create suction. The pump will run continuously but produce no water.

Submersible Pumps: While less common, submersibles can also experience air lock, especially in wells with fluctuating water levels. Air can enter through cracks in the drop pipe, failing check valves, or when the water level drops below the pump intake.

Convertible Jet Pumps: These pumps can operate in either shallow or deep well configurations and can experience air lock in either setup. The deep well configuration with an ejector assembly is particularly vulnerable to air intrusion.

Signs Your Well Pump Is Air Locked

Recognizing an air lock quickly is important—the longer a pump runs without water, the more likely it is to overheat and suffer permanent damage. Look for these telltale signs:

Primary Symptoms

• Pump runs but produces no water: The most obvious sign. You hear the motor running, but nothing comes out when you turn on a faucet.
• Sputtering or spitting at faucets: Bursts of air followed by small amounts of water indicate partial air lock.
• Low or stuck pressure gauge: The gauge shows low pressure (below 20 PSI) or doesn't move at all while the pump runs.
• Pump won't cycle off: Because it can't build pressure, the pump runs continuously without reaching cut-off pressure.
• Unusual pump sounds: A higher-pitched whine or labored sound indicates the pump is moving air instead of water.

Warning Signs of Pump Overheating

• Burning smell near the pump
• Hot pump housing (jet pumps)
• Thermal overload trips repeatedly
• Breaker trips after pump runs for a few minutes

Important: If you notice any overheating signs, turn off the pump immediately. Running a pump dry for more than 30-60 seconds can cause serious damage to the motor windings and seals.

Common Causes of Air Lock

Understanding why air locks happen helps you both fix the current problem and prevent future occurrences:

1. Loss of Prime (Jet Pumps)

Jet pumps must maintain a column of water from the well to the pump. This "prime" can be lost due to:

• Power outages allowing water to drain back
• Failing foot valve that doesn't hold water
• Leaks in the suction line or fittings
• Running the pump with a dry well
• Crack in the pump housing

2. Check Valve Failure

Check valves prevent water from draining back down the well when the pump stops. When these valves fail:

• Water drains back during off-cycles
• Air enters the system each time water drops
• The problem recurs every time the pump restarts

See our guide on check valve replacement for more information.

3. Dropping Water Level

If your well's static water level drops below a critical point:

• Submersible pumps can draw air instead of water
• Jet pump ejectors can lose prime
• This is common during droughts or heavy pumping seasons

Learn about low yield well solutions if this is a recurring issue.

4. Leaks in Drop Pipe or Casing

Cracks or holes in the drop pipe (the pipe connecting the pump to the surface) allow air to enter the system:

• Corroded steel pipes develop pinhole leaks
• PVC pipe joints can fail
• Well casing cracks admit air above the water line

5. Recent Service or Power Outage

Air locks commonly occur after:

• Pump replacement or repairs
• Extended power outages
• Pressure tank service
• Any work that drains the system

How to Clear an Air Lock: Step-by-Step

The clearing method depends on your pump type. Follow these instructions carefully, and don't skip safety steps.

Clearing an Air Lock in a Jet Pump

Tools needed: Wrench, bucket, funnel, clean water (at least 5 gallons)

1. Turn off power: Switch off the pump at the breaker or disconnect. Never work on a pump with power connected.
2. Locate the priming plug: This is typically a square or hex-head plug on top of the pump housing. Some pumps have a priming port with a cap.
3. Relieve pressure: Open a faucet to release any residual pressure in the system.
4. Remove the priming plug: Use a wrench to carefully remove the plug. Some water may spill out—have a bucket ready.
5. Fill the pump housing: Using a funnel, pour clean water into the priming hole. Continue until water overflows—this indicates the housing is full.
6. Check suction lines: While filling, water should flow down into the suction pipe. If it drains away quickly, you may have a leak or failed foot valve.
7. Replace the priming plug: Tighten securely but don't over-torque—you may need to do this again.
8. Restore power and test: Turn on the pump. It should build pressure within 30-60 seconds. If not, repeat the priming process.

Tip: If you need to prime multiple times, or if water drains away quickly when priming, you likely have a leak or failed valve that requires professional repair.

Clearing an Air Lock in a Submersible Pump

Submersible pumps are self-priming but can still air lock. The approach is different:

1. Turn off power: Disconnect at the breaker.
2. Drain the pressure tank: Open a faucet and let the tank empty completely. This removes trapped air from the pressure tank.
3. Check the pressure tank: While empty, check the air charge with a tire gauge on the Schrader valve. It should read 2 PSI below cut-in pressure (typically 28 PSI for a 30/50 system).
4. Close all faucets: Make sure nothing is open in the house.
5. Restore power: The pump should start and gradually build pressure.
6. Bleed air from system: Once pressure builds, open the faucet closest to the pressure tank. Let it run until water flows steadily with no air spurts.
7. Repeat for other faucets: Work through the house, running each faucet until air is cleared.

Clearing Stubborn Air Locks

If standard methods don't work, try these advanced techniques:

Garden Hose Method: Connect a garden hose from a neighbor's water supply to an outside spigot on your system. With your pump off, open the hose valve and let water flow backward through your system for several minutes. This can push air out and restore prime.

Pitless Adapter Bleed: Some systems have a bleeder valve at the pitless adapter (where the pipe exits the well casing). Opening this valve while the pump runs can release trapped air.

Multiple Priming Cycles: For deep wells or long pipe runs, you may need to prime 3-5 times, allowing the pump to run briefly between attempts, to gradually work air out of the system.

When to Call a Professional

While many air locks can be cleared with DIY methods, certain situations require professional service:

• Recurring air locks: If you're clearing air locks more than once a month, there's an underlying problem
• Unable to maintain prime: Water drains away as fast as you add it
• Pump shows signs of damage: Unusual sounds, overheating, or burnt smell
• Well water level issues: If the well is going dry, you need a well inspection
• Check valve or foot valve failure: These require pulling the pipe from the well
• Submersible pump not restarting: May indicate motor damage or control box issues

Preventing Air Locks

Prevention is always better than repair. Follow these strategies to minimize air lock risk:

Maintain Your Check Valves

• Replace check valves every 5-7 years or when they fail
• Install quality brass or stainless steel valves
• Consider dual check valves for added protection

Inspect Your Foot Valve (Jet Pumps)

• Test annually by shutting off pump and monitoring prime
• Replace if water level drops more than a foot overnight
• Use a foot valve with a built-in check

Monitor Water Levels

• Know your well's static and pumping water levels
• Avoid over-pumping during dry seasons
• Consider a low-water cutoff switch for submersibles

Proper System Design

• Ensure correct pipe sizing to prevent air trapping
• Install air release valves at high points in the system
• Avoid excessive horizontal runs without vents

Regular Maintenance

• Schedule annual well system inspections
• Check pressure tank pre-charge quarterly
• Address small leaks before they cause bigger problems

Understanding Pump Cooling and Air Lock Damage

Well pumps rely on the water they pump for cooling. When a pump is air-locked:

Jet Pump Motors: The motor is air-cooled but the pump end seals and impeller depend on water lubrication. Running dry causes rapid seal wear and can warp the impeller housing.

Submersible Motors: These are water-cooled by design. The water flowing past the motor removes heat. Without water flow, motor temperature rises rapidly—damage can occur in under a minute of dry running.

Prevention: Most modern pump controllers include "run dry" protection that shuts off the pump if it detects no flow. If your system lacks this feature, consider upgrading your pump controller.

Frequently Asked Questions