Direct answer
The clearest sign of an air lock is a pump that sounds like it’s running normally while the jets produce little or no water — a pattern Hot Spring and Jacuzzi both describe following a drain and refill. If the motor is on but water flow is weak, surging, or absent, trapped air in the plumbing can be a more likely explanation than a failed pump. Recognizing this pattern matters because the fix for an air lock is different from the fix for a failed pump or motor.
Safety note
Follow your manual for any steps that involve the filter compartment or fill lines. Do not open the equipment compartment, touch wiring, or work on the pump itself — those are technician-level steps if a manufacturer’s homeowner-facing purge method doesn’t resolve it. The checks below are about recognizing the pattern, not disassembling anything.
Signs that point to an air lock
The pump runs, but the jets don’t
Jacuzzi’s guide lists an airlock after refilling among the common, DIY-friendly causes of pump problems, alongside a tripped GFCI, a clogged filter, and low water level (Jacuzzi). The pattern that stands out is a pump that is clearly powered and running while jets stay weak or silent.
It happened right after a drain and refill
Air lock is a plumbing condition, not an electrical fault. Both Hot Spring and Jacuzzi describe it as following a drain and refill of the spa. If your spa was working normally before a refill and jets or heat changed afterward, that timing is itself a strong clue (Hot Spring; Jacuzzi). Jacuzzi’s guide also frames checks like this as a step to take before considering whether the pump itself needs repair or replacement, rather than jumping straight to that conclusion (Jacuzzi).
The spa won’t heat, but jets and lights still respond
Hot Spring’s troubleshooting chart lists “air lock was created after filling the spa” as one of the causes when a spa won’t heat even though jets and lights operate, alongside blinking “Ready” and “Power” logo lights (Hot Spring). If that description matches what you’re seeing, see Hot Tub Has Power but No Heat for the next steps.
Safe checks the homeowner can do
- Note when the symptom started. A recent drain or refill raises the odds of an air lock, since that is the specific trigger Hot Spring and Jacuzzi both describe.
- Listen to the pump while jets are off, then turn jets on. A motor that sounds normal while jets stay weak or silent fits the air-lock pattern described above, rather than a pump that isn’t running at all.
- Check whether flow is weak everywhere or only from certain jets, and note if it surges rather than staying steady.
- Confirm the water level meets your manual’s fill line. Jacuzzi notes low water can also starve flow and trigger a protective shutdown, which can be worth ruling out alongside an air lock.
- Follow your manual’s homeowner-facing purge procedure, such as running water through the filter compartment or standpipe, if your manufacturer documents one for your model. See Hot Tub Not Heating After a Refill for the steps Hot Spring documents for its own spas.
- After purging, run the jets through both low and high speed if available. The Hot Spot Collection guide describes strong, non-surging flow as the sign that air has cleared, and has owners cycle a surging jet off for five seconds before trying it again (Hot Spring Hot Spot Collection guide).
When to stop and call a technician
- Jets stay weak or silent after following your manual’s fill and purge steps
- You would need to open the equipment compartment or work on the pump directly to continue
- The same symptom keeps returning after every refill
- The spa also won’t heat and flow-related checks haven’t resolved it — see Hot Tub Has Power but No Heat
- The pump makes noise you haven’t heard from it before, beyond a normal running hum
A recurring air lock or noise that doesn’t fit the pattern above is worth having a technician look at, since it may point to a plumbing or pump issue rather than simple trapped air.
For general first checks on a spa that isn’t heating, see Hot Tub Not Heating: What to Check First.