A hot tub airlock is a pocket of air trapped in the pump or plumbing, usually right after you drain and refill. The pump hums but the jets barely move, and the heater will not run because water is not flowing past it. The fix is almost always the same: let the control’s priming mode cycle each pump, open the jets and air controls, and if that fails, cut power and bleed the trapped air at the pump union.
What a hot tub airlock is and why refills cause it
Canadian Spa Company describes an airlock as a large pocket of air trapped within the pipework that stops water from flowing properly through the heater (Canadian Spa Company, How to Remove an Airlock).
Leslie’s notes that air commonly gets trapped any time a tub is drained for cleaning, and that the pump then cannot prime (Leslie’s, How to Fix Hot Tub Air Lock).
Signs of a hot tub airlock
- Pump runs, jets do not. You hear the motor, but water barely trickles or only sputters out.
- Error codes about flow or a dry heater. Canadian Spa Company lists “dr” or “HH” as signs of an airlock. The Balboa TP500 and TP500S user guide lists trapped air among its flow related checks for messages such as HFL, LF and dr.
- No heat. With poor flow, the control keeps the heater off. Our guide to a hot tub not heating covers the other causes.
- One pump works, another does not. On two pump tubs, each pump can airlock on its own.
Hot tub pump not circulating? Rule out the easy things first
Balboa’s flow related checks list low water level, suction restrictions, closed valves, trapped air, too many closed jets and pump prime. So before opening a cabinet, confirm the water is at your manual’s fill level, the slice valves are fully open, the jets and air controls are open, and the filter is not clogged (see how to clean hot tub filters).
Use hot tub priming mode the right way
Many spas, including tubs with Balboa controls, enter a priming mode every time power is restored. According to the Balboa TP500/TP500S guide, priming mode lasts about 4 to 5 minutes and the heater is disabled the whole time. Press Jets once for low speed and again for high, then Jets 2 or Aux for a second pump.
Balboa’s limits:
- If water is not flowing from the jets after 2 minutes, turn the pump off and repeat.
- Switching the pump off and on can help it prime, but do not do it more than 5 times.
- Never let a pump run unprimed past the end of priming mode.
- If a pump still will not prime, shut off power to the spa and call for service.
Canadian Spa Company’s start up instructions are stricter: the display shows “Pr” for a 5 minute priming routine, and you should not run a pump for more than 1 minute without moving water. If nothing moves, turn the power off and do the air lock procedure (Canadian Spa Company, Starting Your Hot Tub). Their airlock article suggests pressing Jets 1 on and off a few times during “Pr”, but notes a circulation pump cannot be cleared this way.
How to bleed air from a hot tub, step by step
If priming mode and the easy checks do not get water moving, bleed the pump directly. Canadian Spa Company and Leslie’s describe the same method; your owner’s manual wins where it differs.
- Turn off the spa at the breaker or GFCI.
- Remove the cabinet panel that gives access to the pump attached by plumbing to the control pack.
- Find the pump unions. Two pipes enter the pump, held by large union nuts. Canadian Spa Company says to work on the higher of the two.
- Slowly loosen that union by hand or with channel lock pliers.
- Retighten as soon as water flows. Snug it until it stops dripping.
- Restore power and run the jets during priming mode to confirm strong flow.
- Repeat for each pump that is not moving water, then check every union for drips before closing the cabinet.
Leslie’s notes some newer tubs have a dedicated bleeder valve, so check your manual first.
Safety while you work
Kill power at the breaker before touching a union and never bypass the GFCI. If the GFCI keeps tripping or anything in the control pack looks wet or burnt, stop. Electrical diagnosis is a job for a licensed electrician or spa technician, and local code has the final word on wiring.
How to refill a hot tub without an airlock
Canadian Spa Company’s start up instructions say to remove the filter cartridge and fill through the filter housing, which they say prevents an air lock in the pumps. Master Spas gives the same advice (Master Spas, How to Fill Your Hot Tub).
| Refill step | Why it helps | Source |
|---|---|---|
| Keep power off until full | Pumps never start dry | Canadian Spa Company |
| Open all valves and jets before filling | Lets air escape the plumbing as water rises | Balboa TP500/TP500S guide |
| Fill through the filter housing | Fills the lines first and pushes air out | Canadian Spa Company, Master Spas, Leslie’s |
| Check pump unions are tight | Fittings can loosen in transport | Master Spas |
| Cycle each pump in priming mode | Purges remaining air before the heater runs | Balboa, Master Spas |
Once water is moving, balance and sanitize as usual. Our hot tub startup chemicals guide covers the first fill order, and the hot tub maintenance schedule covers how often to drain.
When to call a technician
Call for service if a pump will not prime after the union is bled, if a union keeps leaking after you retighten it, if the pump hums but the shaft does not spin, or if flow codes return after the water is clearly moving.
Canadian Spa tubs we carry and their pump setups
Each pump may need priming, so pump count matters. Specs are from our listings; all list Balboa controls. See the full Canadian Spa Company lineup or start with our hot tub buying guide.
| Model | Electrical | Pumps | Water | Price |
|---|---|---|---|---|
| Yukon 2-Person 16-Jet | 120V 15A | One 2 speed 2 HP | 350 L | $7,749 |
| Calgary 4-Person 24-Jet | 120V 15A | One 2 speed 2 HP | 700 L | $8,449 |
| Richmond 6-Person 27-Jet | 120V 15A | One 2 speed 2 HP | 900 L | $10,249 |
| Toronto SE 6-Person 44-Jet | 240V 50A | Two 2 speed 5 HP | 1,110 L | $12,749 |
| Burnaby 6-Person 44-Jet | 240V 50A | Two 2 speed 5 HP | 1,100 L | $13,249 |
| Kingston 7-Person 53-Jet | 240V 60A | Three 2 speed 5 HP | Not listed | $18,749 |
After a refill, the Canadian Spa Company test strips ($24.99 for 50) check chlorine, pH and alkalinity.
Frequently asked questions
How do I bleed air from a hot tub?
First try priming mode with all jets and valves open. If water still will not flow, cut power at the breaker and slowly loosen the higher pump union until water flows, then retighten.
Why is my hot tub pump not circulating after a refill?
Most often it is trapped air. Also check water level, slice valves, closed jets and the filter.
How long does hot tub priming mode last?
On Balboa TP500 series panels, about 4 to 5 minutes, with the heater disabled. Canadian Spa Company’s start up guide lists 5 minutes. Check your own manual.
Can an airlock damage my pump?
It can. Canadian Spa Company warns that running a pump with an air lock or without water can cause permanent damage that its warranty does not cover.
Need help with your hot tub?
Call us at 866-777-2590, Monday to Friday, 9AM to 6PM PST. Orders of $999 or more ship with free freight shipping, and orders below that ship for a $200 flat rate. See our return and refund policy for details.
