Sep 18, 2026

How to Clear a Hot Tub Air Lock: Spa Pump & Arctic Spas Guide

Hot Tub Air Locks and Information

If your hot tub pump is running but little or no water is coming from the jets—especially immediately after draining and refilling the spa—you most likely have an air lock.

Air locks are an unfortunate inevitability of spa ownership. Every spa is susceptible to an air lock, particularly when the spa is first filled or after the spa has been drained and refilled. Fortunately, an air lock usually does not mean anything is broken, and in most cases it can be cleared fairly quickly.

Quick Fix: How to Clear an Air Lock From a Spa Pump

If you just want to get your spa running again, start here.

Turn the spa power off at the breaker.
Make sure the spa is completely full. The water should be at its normal operating level and well above the filter intakes. (generally filled to just underneath the pillows)
Make sure all pump valves are open. If your spa has slice valves or ball valves near the pump, they must be fully open. (If your spa was just delivered by Premier, the valves will be open)
Turn the spa back on and briefly try the affected pump. Cycle the pump from off to on or from low to high speed if applicable. If strong water flow immediately returns, the pump has primed.
If the pump runs but still does not move water, turn the breaker back OFF. Do not leave a pump running without water flow.
Locate the affected pump and slightly loosen one of the large pump union nuts. You only need to loosen it enough to allow trapped air to escape. Do not completely remove the union.
Listen for air escaping. You may hear a hiss or see air and water sputter from the connection.
Once a steady stream of water appears, tighten the union back up. Make it snug, but do not overtighten the plastic fitting.
Restore power and turn the pump on again. You should now have strong, consistent water flow from the jets.

If your spa has multiple jet pumps, each pump can air lock independently. One pump may work normally while another pump runs without moving any water.

What Is a Hot Tub Air Lock?

A spa pump air lock occurs when a pocket of air becomes trapped in the plumbing or inside the wet end of the pump and prevents the pump from establishing normal water flow.

The pump motor may still be running and the impeller may still be spinning, but instead of being completely surrounded by water, the pump is trying to move trapped air.

Typical symptoms of a spa air lock include:

The pump runs or hums but the jets do not move water.
Only a small amount of water comes from the jets.
The jets surge between strong and weak flow.
The problem began immediately after draining and refilling the spa.
A FLO, FL, low-flow, or similar flow error appears.
The spa stops heating because the control system cannot confirm adequate water flow.

An important distinction: if the pump motor does not run at all, the problem may not be an air lock. An air-locked pump generally runs but cannot establish proper water flow.

Video: How to Bleed or “Burp” an Air-Locked Spa Pump

The process of releasing trapped air from the pump is sometimes called bleeding, burping, or priming the pump.

How to Clear an Air Lock on an Arctic Spa

Arctic Spas are susceptible to pump air locks just like every other hot tub. They occur most commonly immediately after a drain, clean, and refill.

The easiest approach is to first determine which pump is not moving water. On a multi-pump Arctic Spa, Pump 1 may be operating normally while Pump 2 or Pump 3 is air locked.

Step 1: Try Priming the Arctic Spa Pumps

After filling an Arctic Spa, activate each pump and check for strong, consistent water flow.

Pump 1: Turn Pump 1 to high speed and allow it to operate for approximately 1 minute.
Pump 2: If equipped, activate Pump 2 and allow it to operate for approximately 1 minute.
Pump 3: If equipped, activate Pump 3 and allow it to operate for approximately 1 minute.
Additional pumps: Activate them individually and verify water flow.

Strong, non-surging jets indicate that the pump is properly primed.

If the jets are weak or surging, also verify that the spa has enough water and that the filters are not restricting flow.

For complete Arctic Spa startup instructions, see our New Arctic Spa Owner Guide.

Step 2: Bleed the Air From the Arctic Spa Pump

If the pump motor is operating but it is still not moving water:

Turn OFF power to the spa at the breaker.
Remove the cabinet access panel necessary to reach the affected pump.
Locate the large plumbing union attached to the wet end of the pump.
Carefully loosen the union just enough to release the trapped air. You may hear a noticeable hiss.
Allow the air to escape until water begins coming from the union without large pockets of air.
Retighten the union until it is snug. Do not overtighten it.
Restore power to the spa.
Turn on the affected pump and confirm strong, consistent jet flow.

Only a small amount of loosening is normally required. Do not completely remove the pump union while the spa is full.

Arctic Spas Air Lock Video

Arctic Spa FLO Error After a Drain and Refill

An air lock can also cause an Arctic Spa to display a FLO or low-flow error. The spa's control system monitors water flow because the heater should not operate without adequate water moving through it.

If a pump is air locked, the pump may be spinning but there may not be enough actual water movement through the heater. The control system may therefore prevent the heater from operating until normal flow is restored.

A FLO error does not automatically mean you have an air lock. Restricted filters, low water level, closed valves, blocked plumbing, and other circulation problems can produce similar symptoms.

If you have already confirmed that the pump is not air locked and the filters are not causing the problem, see our Arctic Spas Blocked Pump Flow: Not an Air Lock or Dirty Filters troubleshooting guide.

How to Prevent Spa Air Locks When Refilling

You cannot completely eliminate the possibility of an air lock. Every spa is susceptible to them. However, you can reduce the likelihood of one occurring by filling the plumbing correctly.

Fill the Spa Through the Filter Area

Instead of dropping the garden hose directly into the footwell of the spa, place the hose in the filter compartment or filter opening while refilling.

This helps introduce water into the suction-side plumbing as the spa fills and can push some of the air out of the plumbing before the pump is started.

For Arctic Spas, Premier Pool & Spa recommends removing the filter and filling through the area where the filters install. The filters can then be reinstalled once the spa is full.

See our complete How to Drain and Refill Your Hot Tub guide before your next water change.

Why Does Filling Through the Filter Area Help?

When you drain a hot tub, the visible spa shell becomes empty—but the plumbing does not become filled with “nothing.” The plumbing becomes filled with air.

When you refill the spa, water needs to displace that air.

If the spa is simply filled from the footwell, water can rise around the plumbing while pockets of air remain trapped inside suction lines, return lines, plumbing loops, and the pump wet end.

Filling through the filter area encourages water to enter the pump's suction plumbing earlier in the refill process, which can help push trapped air through the system.

Why Can an Air Pocket Stop a Powerful Spa Pump?

This is one of the more interesting parts of spa hydraulics.

A spa pump is designed to move water. Water is essentially incompressible under normal spa operating conditions. Air behaves very differently because it is highly compressible.

If the pump wet end fills with air instead of water, the spinning impeller may simply churn and compress the trapped air rather than establishing the continuous water flow that the plumbing system requires.

You can think of the trapped air pocket somewhat like a temporary blockage or kink in a hose. The plumbing itself may be completely open, but the pump cannot establish the solid column of water it needs to move water through the heater and back to the jets.

Why Does Air Get Trapped in Spa Plumbing?

Hot tubs contain a surprisingly complicated network of plumbing.

Lines travel:

Up toward jets in the spa shell
Down toward pumps and equipment
Around seats
Through manifolds
Through heaters
Back toward dozens of individual jets

Air naturally rises toward high points in these plumbing runs.

If a section of plumbing rises and then drops again, it can create a natural location where an air pocket becomes trapped. This is sometimes called a high-point air trap.

That is one reason an air lock can happen even when the spa appears to be completely full of water.

Why Does Loosening the Pump Union Fix an Air Lock?

When you slightly loosen the union on an air-locked pump, you are effectively creating a temporary bleed or vent point.

The trapped air now has somewhere to escape.

You may first hear:

Hiss → sputter → water flow.

Once the trapped air leaves, water can move into the pump wet end and replace the air pocket. After the union is tightened again, the pump can establish normal water flow.

This is why technicians sometimes refer to the process as “burping” the pump.

For the Curious: The Technical Hydraulics Behind an Air Lock

You absolutely do not need to watch the following video to fix an air lock on your spa.

This is an extremely technical explanation of air locks and fluid-system hydraulics. However, if you are interested in understanding why air locks exist and what is physically happening inside your spa's plumbing, it is a fascinating explanation.

Four Useful Ways to Think About Spa Air Locks

1. The “Empty Pipe” Refill

When a spa is drained, the plumbing does not truly become empty—it becomes full of air.

As the spa is refilled, incoming water has to displace all of that air. Depending on the plumbing layout, some of the air may instead be pushed deeper into the plumbing and toward the pump.

2. The Invisible Blockage

An air pocket can behave somewhat like an invisible restriction in the plumbing.

Because air compresses while water essentially does not, the pump impeller may spin inside an air-filled pump housing without establishing the solid water flow necessary to push water through the heater, plumbing, and jets.

3. The High-Point Trap

Spa plumbing does not travel in perfectly straight horizontal lines. It rises and falls throughout the cabinet and spa shell.

Air naturally rises, so bubbles can collect at the highest points of these plumbing loops and remain trapped there as the spa fills.

4. The Bleed-Valve Principle

Many fluid systems use bleed valves or vents to remove trapped gas.

Loosening a spa pump union accomplishes essentially the same thing: it gives the trapped air a path out of the system. Once the air escapes and water reaches the pump, normal circulation can resume.

What If Clearing the Air Lock Does Not Fix the Spa?

If the pump has been properly bled but you still have little or no water flow, do not continue assuming the problem is an air lock.

Check for:

Dirty or plugged filters
Low spa water level
Closed slice or ball valves
Debris blocking the pump intake
A damaged pump impeller or wet end
A pump motor that is not actually running
A flow or pressure sensor problem
Another plumbing restriction

Arctic Spa owners can also review our Blocked Arctic Spa Pump Flow Troubleshooting Guide.

Frequently Asked Questions About Spa Air Locks

Are Air Locks Normal in Hot Tubs?

Yes. Air locks are an unfortunate reality of spa ownership, and every hot tub is susceptible to them. They are especially common immediately after draining and refilling the spa.

Does an Air Lock Mean My Spa Pump Is Bad?

Usually not. If the pump motor runs but water does not move through the jets, trapped air may simply be preventing the pump from priming.

Can an Air Lock Cause a FLO Error?

Yes. An air-locked pump may not provide sufficient water movement for the spa's flow or pressure monitoring system, which can trigger a FLO or similar error and prevent the heater from operating.

Can One Spa Pump Be Air Locked While the Others Work?

Yes. Each jet pump has its own plumbing circuit, so one pump may be properly primed while another pump contains trapped air.

Can I Damage a Spa Pump by Running It Air Locked?

Potentially. A spa pump relies on water moving through the wet end during normal operation. If the pump is running but not moving water, shut it off and correct the priming problem rather than allowing it to continue operating dry.

Why Does My Spa Get an Air Lock Every Time I Refill It?

Your plumbing configuration may naturally trap air during filling. Filling the spa through the filter compartment rather than directly into the footwell can substantially reduce the amount of air left in the suction plumbing.

Should I Remove the Filters When Troubleshooting an Air Lock?

If you have weak or surging flow rather than no flow at all, temporarily removing the filters can help determine whether the filters are restricting circulation. If normal flow returns with the filters removed, clean or replace the filters rather than continuing to troubleshoot an air lock.

Related Arctic Spa & Hot Tub Guides

How to Drain and Refill Your Hot Tub – Proper draining, cleaning, refilling, and filter maintenance.
Your New Arctic Spa – Startup procedures, controls, filtration, water care, and other important owner information.
Arctic Spas Blocked Pump Flow – Troubleshooting when the problem is not an air lock or dirty filter.
Arctic Spa Classic & Core Series Filter Guide – Filter types, replacement intervals, and troubleshooting restricted flow.

Still having trouble? If the pump has been properly primed but your spa still does not have normal water flow, contact Premier Pool & Spa for additional troubleshooting or spa service.