Well Pump Air Lock: What It Is & How to Fix It

What Is Air Lock in a Well Pump System?

Air lock is one of the most frustrating well problems homeowners encounter—your pump is running, you can hear it working, but little or no water comes out of your faucets. What's happening is that a pocket of air has become trapped inside the pump housing, the drop pipe, or the plumbing lines, and that air bubble is blocking water from flowing normally through the system.

Think of it like trying to pour water from an upside-down bottle. The water wants to come out, but air can't get in to replace it, so nothing moves. In a well system, trapped air creates a similar blockage. The pump impeller spins but can't grab water because it's spinning in air instead. Or air trapped at a high point in the piping creates a vapor lock that water pressure alone can't push through.

How to Recognize Air Lock

Air lock presents with a distinctive set of symptoms that are easy to identify once you know what to look for:

• No water or very weak flow — You turn on a faucet and get nothing, or just a trickle. This is the most obvious sign, especially if it happens suddenly rather than gradually.
• Sputtering and spitting faucets — Instead of a steady stream, water comes out in bursts mixed with air. You'll hear a characteristic "pfft-pfft-pfft" sound as air and water alternate.
• Pump runs continuously without building pressure — Check your pressure gauge at the tank. If the pump is running but pressure isn't climbing toward the cut-off point (typically 50-60 PSI), air lock is a likely culprit.
• Explosive air bursts — When you open a faucet, a loud burst of air blasts out, sometimes violently enough to splash water across the sink. This indicates a large volume of trapped air.
• Pressure gauge fluctuations — The pressure reading bounces erratically rather than climbing steadily, indicating the pump is alternately catching water and then losing it to air.

Which Pump Types Are Affected?

Not all well pump configurations are equally vulnerable to air lock:

Jet pumps are the most susceptible by far. Because jet pumps sit above ground and pull water up through suction, they depend on maintaining a sealed, air-free suction line. Any air that enters the suction side disrupts the pump's ability to create the vacuum it needs to lift water. Shallow-well jet pumps (single-pipe) and deep-well jet pumps (two-pipe) are both vulnerable, though deep-well configurations have more joints and connections where air can infiltrate.

Centrifugal and booster pumps can also air lock, particularly if they're installed at a point where air can accumulate in the intake line. These above-ground pumps rely on priming—having their impeller housing full of water—to function. If air displaces that water, the pump loses its ability to move water.

Submersible pumps rarely experience true air lock because they operate fully submerged at the bottom of the well. However, air can still accumulate in the piping above a submersible pump, and if the well's water level drops below the pump intake, the pump can draw air instead of water—which creates similar symptoms and can damage the pump motor if it continues.

What Causes Air Lock in Well Systems

Air doesn't just appear in your well system randomly. There's always a source, and finding that source is the key to preventing recurrence. Here are the five most common causes we encounter when diagnosing air lock problems across San Diego and Riverside Counties:

1. Lost Prime (Jet Pumps)

This is the number one cause of air lock in jet pump systems. "Prime" refers to the water that fills the pump housing and suction line—without it, the pump can't create the suction needed to pull water from the well. Prime is lost when air replaces water in the suction line, and it happens for three main reasons:

• Suction line leak — Even a pinhole leak in the suction pipe allows air to be drawn in while the pump runs. The leak may be so small that you never see water dripping out, but the pump's suction is strong enough to pull air in through the tiniest imperfection.
• Low water level — If the water level in your well drops below the suction pipe intake or the foot valve, the pump draws air instead of water. This is common during drought or when multiple wells on the same aquifer are pumping simultaneously.
• Failed foot valve — The foot valve sits at the bottom of the suction line and is designed to hold water in the pipe when the pump shuts off. When a foot valve fails, water drains back down into the well between pump cycles, and air fills the void.

2. After System Maintenance or Repairs

Any time your well system is opened up—whether for a pump replacement, pipe repair, filter change, or pressure tank service—air enters the lines. This is completely normal and expected. The key is properly purging that air before resuming normal operation. Common scenarios include:

• Pipes drained for repairs — When a plumber drains lines to fix a leak or replace a section, the entire system fills with air that must be bled out afterward.
• New pump installation — A brand new pump needs to be primed and the entire pipeline needs air purging before the system will operate normally.
• Filter cartridge changes — Opening a filter housing, even briefly, introduces air into the system. This is one of the most common triggers for minor air lock that homeowners encounter regularly.

3. Power Outages

When power goes out, the pump stops but water in the pipes may continue flowing under gravity—especially in systems without properly functioning check valves. As water drains back toward the well, air enters through any high points or faucets that were open. When power returns, the pump encounters air instead of solid water in the lines.

This is particularly problematic in systems with worn or missing check valves. A properly installed check valve prevents backflow and maintains the water column in the drop pipe. If your system frequently air-locks after power outages, worn check valves are almost certainly the culprit.

4. Declining Water Level

During prolonged drought or periods of heavy usage, the water level in your well can drop low enough for the pump to suck air. In San Diego County, this is especially common during late summer and fall after months without significant rainfall. The symptoms are cyclical—you'll notice sputtering and air when water demand is high (morning and evening), but it may clear up during low-use periods when the well has time to recover.

If your well is drawing down to the pump level, you have a yield problem that needs to be addressed. Continuing to pump air can damage your pump motor and shorten its lifespan significantly. A low-water cutoff switch is an inexpensive safeguard that shuts the pump off before it starts drawing air.

5. Suction Line Leaks (The Hidden Air Source)

This is the most insidious cause of air lock because suction-side leaks can be nearly invisible. Unlike a pressure-side leak where water sprays out, a suction-side leak draws air in while the pump runs. The leak might be at a threaded connection, a cracked fitting, or even a corroded section of pipe. You won't see water leaking out—the only evidence is air in your water and repeated priming failures. Finding suction leaks often requires a pressure test on the suction line with the pump disconnected.

How to Fix Air Lock: Step-by-Step Instructions

The good news is that most air lock situations can be resolved by the homeowner without calling a professional. The approach depends on your pump type and the severity of the problem.

For Most Systems: Bleeding the Air

This method works for any well system where air has accumulated in the house-side plumbing. The principle is simple: open faucets starting from the highest point in the system and let the air escape naturally as water pushes it out. Here's the process:

1. Turn off the pump at the circuit breaker if it's currently running. Running a pump against air lock wastes electricity and can overheat the motor.
2. Open the highest faucet in your house — this is usually an upstairs bathroom faucet or the highest shower head. Open it fully, both hot and cold. Air rises, so starting high gives it the easiest escape path.
3. Turn the pump back on at the breaker. You should hear it start running.
4. Wait for water to reach the faucet. It will start as sputtering bursts of air mixed with water. This is normal—the air is being pushed out. Don't close the faucet yet.
5. Let it run until the flow becomes steady with no more air bursts. This might take anywhere from 30 seconds to several minutes depending on how much air was in the system.
6. Close that faucet and move to the next highest one. Open it and run until steady. Work your way down through the house—bathrooms, kitchen, laundry, outdoor spigots.
7. Don't forget the hot water side. Air can also be trapped in the hot water lines between the water heater and faucets. Run each hot water faucet until flow is steady.
8. Check your pressure gauge at the tank. It should now cycle normally between your cut-in and cut-out pressures (typically 30/50 or 40/60 PSI).

For Jet Pumps: Priming Procedure

Jet pumps require a full column of water in the pump housing and suction line to operate. If the pump has lost prime (the most common cause of jet pump air lock), bleeding faucets alone won't solve it—you need to refill the pump with water first. Here's how:

1. Turn off power at the breaker. Never work on a pump with power connected.
2. Locate the priming plug on top of the pump housing. It's usually a large hex-head plug or square plug, sometimes made of plastic.
3. Remove the plug and pour clean water into the pump housing. Use a funnel to avoid spilling. Fill it until water reaches the opening and you can see it.
4. Replace the priming plug and tighten securely. A loose plug will let the pump suck air right at the housing.
5. Turn power back on and listen carefully. You should hear the pump catch within 30-60 seconds—the sound changes from a whiny, struggling pitch to a smoother, loaded tone as it starts moving water.
6. If the pump doesn't catch after 60 seconds, turn it off immediately to prevent overheating. Repeat the priming process—it may take 2-3 attempts, especially if the suction line was completely drained.
7. Once the pump catches, open a nearby faucet and verify steady water flow before considering the job done.

Pro tip: If a jet pump repeatedly loses prime, don't just keep re-priming. There's an air leak somewhere—either in the suction line, at a fitting, or the foot valve has failed. Find and fix the source, or you'll be priming again within hours or days.

Dealing with Stubborn Air Lock

Sometimes air is trapped at a point in the system that won't clear with normal faucet bleeding. In these cases, try these additional approaches:

• Drain the pressure tank — Open the boiler drain (spigot) at the bottom of your pressure tank to release trapped air from the tank itself. Some pressure tanks have an air release valve at the top that serves this purpose.
• Disconnect and refill manually — For severely air-locked lines, you may need to disconnect a union fitting at a high point in the piping and pour water in from that point to displace the air pocket.
• Check for the air source — If air keeps returning after you clear it, stop trying to bleed and start looking for the entry point. A persistent air source means there's a leak, a failed valve, or a low-water condition that needs to be addressed.

Submersible Pump Systems

If you have a submersible pump and you're getting air in your water, it's almost never a traditional air lock. Submersible pumps operate at the bottom of the well, fully submerged, so they can't draw air under normal conditions. If air is entering a submersible system, it points to one of these more serious issues:

• Falling water level — The most common cause. If the well's static water level has dropped below the pump intake, the pump is literally sucking air from the well bore. This needs immediate attention—running a submersible pump in air will burn out the motor.
• Drop pipe leak — A crack or loose connection in the drop pipe (the vertical pipe connecting the pump to the surface) can allow air to enter the water stream. This usually requires pulling the pump to inspect and repair.
• Failed check valve — If the check valve above the pump has failed, water may cascade back down after the pump shuts off, creating air pockets in the piping as it flows back.

Preventing Air Lock: Long-Term Solutions

Clearing an air lock is a temporary fix. If air keeps getting into your system, you need to address the underlying cause. Here are the most effective preventive measures:

Install and Maintain Check Valves

Check valves are your first line of defense against air entering the system during pump-off cycles. For jet pump systems, a foot valve at the bottom of the suction line holds the water column in place when the pump shuts off. For submersible systems, a check valve at the wellhead (and sometimes additional valves down the well) prevents the water column from draining back into the well.

Check valves don't last forever. A typical brass foot valve may last 5-10 years before the flapper seal wears enough to leak. If your system loses prime overnight or after every power outage, a worn check valve is the most likely cause. Replacement is straightforward for surface-mounted check valves but requires pulling the pump for in-well valves.

Eliminate Suction Line Leaks

For jet pump systems, the suction line is the most common air entry point. Inspect all threaded connections, fittings, and pipe joints on the suction side. Use Teflon tape and pipe dope together on threaded connections for a reliable seal. If the suction line is galvanized steel and more than 20 years old, consider replacing it with PVC or polyethylene—older steel pipe develops pinhole corrosion that's nearly impossible to find and fix.

Install a Low-Water Cutoff Switch

If your well has marginal yield or you've experienced dry-down during summer months, a low-water cutoff switch is one of the best investments you can make. This sensor detects when the water level drops below a safe threshold and shuts the pump off before it starts drawing air. It protects both your pump (running dry destroys motors) and prevents air from entering the system. The pump automatically restarts when the water level recovers. These switches typically cost $100-200 installed and can save you thousands in pump replacements.

Post-Power-Outage Protocol

If your area experiences frequent power outages, develop a routine for when power returns. Before running the dishwasher or washing machine, open a faucet and check for steady flow. If you hear sputtering, bleed the air from the highest faucet first. Consider installing a whole-house surge protector to protect your pump controller from power surges that often accompany outage/restoration cycles.

After Any System Service

Make air bleeding part of your post-service checklist. Every time you change a filter cartridge, work on plumbing, or have any pump service done, plan to run each faucet (hot and cold) until flow is steady. For jet pumps, always verify the prime after any work on the system—even work that seems unrelated to the pump itself. Air finds its way into the most unexpected places.

Frequently Asked Questions

What is air lock in a well pump?

Air lock occurs when a pocket of air becomes trapped inside the pump housing, drop pipe, or household plumbing lines, blocking the normal flow of water. The pump motor runs and sounds like it's working, but it's spinning against air instead of water, so little or no water reaches your faucets. It's one of the most common reasons well owners suddenly lose water, and fortunately, it's usually one of the easiest to fix.

How do I get air out of my well system?

Start by opening the highest faucet in your house (usually an upstairs bathroom) and let it run. The water will sputter and spit at first as air is pushed out. Keep it running until the flow becomes smooth and steady—this can take anywhere from 30 seconds to several minutes. Then close that faucet and open the next highest one, working your way down through the house. Don't forget to run both hot and cold at each location. For jet pumps that have lost prime entirely, you'll need to reprime the pump first by filling the pump housing with water through the priming plug.

Why does my well pump keep losing prime?

Repeated prime loss almost always points to an air leak on the suction side of the system. The three most common culprits are: a leaking suction line (even a tiny crack or loose fitting allows air in), a worn foot valve that lets water drain back when the pump shuts off, or a declining water level that periodically exposes the suction pipe intake. If you're repriming your jet pump more than once a month, it's time to systematically check each of these components. A pressure test on the suction line can quickly identify hidden leaks.

Can submersible pumps get air locked?

True air lock in submersible pump systems is rare because the pump operates submerged in water at the bottom of the well. However, air can still enter submersible systems if the water level drops below the pump intake, if there's a crack or loose connection in the drop pipe, or if the check valve above the pump fails and allows the water column to drain back. If you're getting persistent air from a submersible system, it usually indicates a more serious problem than simple air lock and warrants professional diagnosis.

How long does it take to clear air lock?

A typical air lock can be cleared in 5-15 minutes by systematically bleeding each faucet in the house. Minor air lock from a filter change might clear in under a minute. However, if the air won't clear after 15-20 minutes of bleeding, or if it returns within hours of clearing, there's an active air source that needs to be found and repaired. Continuing to bleed without fixing the source is like mopping a floor without fixing the leak in the ceiling.

Is air lock dangerous for my well pump?

Air lock itself won't immediately damage your pump, but running a pump against air lock for extended periods can cause overheating—especially in submersible pump motors that rely on water flow for cooling. Jet pump motors have thermal overload protection that should shut them off before overheating, but repeatedly tripping this protection stresses the motor. If your pump can't clear the air lock within a few minutes of operation, shut it off and troubleshoot rather than letting it run indefinitely.

When should I call a professional for air lock?

Call a well service professional if: the air lock won't clear after multiple attempts at bleeding and priming, the air returns within hours or days of clearing, you hear unusual noises from the pump, or you suspect the issue is related to a declining water level. If you've been re-priming a jet pump more than once a week, or if a submersible system is producing air, these situations typically require diagnosis and repair that goes beyond what most homeowners can handle. At Southern California Well Service, we troubleshoot air entry issues, test suction lines, replace check valves, and address the root cause so the problem doesn't keep coming back.