Understanding Air Lock Problems
Air locks occur when air becomes trapped in your hot tub's plumbing or pump, preventing water from circulating properly. The pump runs but moves little or no water because air—which pumps cannot effectively move—occupies space that should contain water. This common problem frustrates owners who hear their pump operating but see no flow from jets or returns.
Air locks typically develop after draining and refilling, after pump replacement or service, or sometimes from suction-side air leaks during normal operation. Understanding why air locks occur helps you both fix current problems and prevent future occurrences. The good news: most air locks resolve with simple procedures requiring no professional service.
Recognizing Air Lock Symptoms
The classic air lock symptom is a running pump producing little or no water flow. You may hear the motor humming normally while jets produce no pressure or only sputter intermittently. The pump may sound somewhat different than usual—higher pitched or laboring—as it struggles against trapped air rather than moving water smoothly.
Other indicators include error codes on your control panel indicating flow problems, heater shutdowns triggered by flow switch safety features, and visible air bubbles in any water that does flow intermittently. If your spa was working fine before draining, service, or other disruption, air lock is a likely cause of subsequent flow problems.
Post-Fill Air Lock Prevention
The most effective approach is preventing air locks during refilling rather than fixing them afterward. When filling your spa, place the hose inside the filter housing or through the filter opening rather than filling from the main spa cavity. This approach fills plumbing from below, displacing air upward through the spa rather than trapping it in pipes.
Fill slowly to allow air adequate time to escape through the rising water. Rushing the fill process can trap air pockets that become problematic when pumps activate. Patience during filling typically eliminates the need for air lock remediation afterward—time invested in proper filling saves time troubleshooting later.
Bleeding Air Through Pump Unions
The most reliable air lock solution involves releasing air directly from the pump. Locate the union fittings connecting plumbing to your pump—these threaded connections can be loosened slightly to release trapped air. With the pump off, very slowly loosen the union on the discharge (output) side of the pump until you hear air hissing out.
Continue loosening gradually until water begins seeping from the connection, indicating air has escaped and water has replaced it. Immediately retighten the union before significant water escapes. This procedure typically requires only quarter-turn loosening to release air. Be prepared with towels for the small amount of water that escapes during the process.
Using Bleed Valves
Some spas feature dedicated bleed valves specifically designed for air lock release. These valves, typically small screws or petcocks on pump housings or nearby plumbing, open to release air without loosening pipe unions. Consult your owner's manual to identify whether your spa has bleed valves and where they're located.
If equipped, open the bleed valve with the pump off. Listen for air escaping, then close the valve once water appears. Try operating the pump; if flow doesn't resume, repeat the bleeding process. Multiple cycles may be needed to clear all trapped air from complex plumbing configurations.
Priming Through Jet Operation
Sometimes activating pumps in specific sequences helps prime the system and clear air locks. Start with the pump on low speed if variable speeds are available—the gentler action may pull water through where high-speed operation cannot. Let low speed run for several minutes before trying higher speeds.
Activating jets individually or in groups may help by changing flow patterns that move trapped air. Close all air controls that inject air into jets, as additional air introduction works against your clearing efforts. If your spa has diverter valves directing flow to different jet groups, manipulating these positions while pumps run may shift air to locations where it can escape.
Gravity Assist Methods
For stubborn air locks, temporarily raising the spa's water level may help. Higher water creates greater pressure head that can force air through the system. Fill the spa several inches above normal operating level, then attempt pump operation. The additional pressure may push air through restrictions where normal water level couldn't.
Similarly, submerging jets or returns that are normally above water line during filling can prevent air from entering or help expel trapped air. Some spas have design features where certain jets are positioned to assist air removal—water flowing from these specific jets indicates successful priming even while others remain affected by residual air.
When to Suspect Other Problems
If standard air lock procedures don't restore flow, other problems may exist. Clogged impellers, closed valves, or pump failures can produce symptoms similar to air lock. Suction-side air leaks can continuously introduce air, creating recurring air lock that's actually ongoing air ingestion rather than trapped air from a single event.
Persistent problems after multiple clearing attempts warrant professional diagnosis. Continuing to run pumps that aren't moving water risks overheating damage. If your efforts don't succeed within a few attempts, stop pump operation and consult with spa service providers who can diagnose whether air lock persists or whether other issues require attention.
Preventing Future Air Locks
Beyond proper filling technique, preventing air locks involves maintaining system integrity that keeps air out during normal operation. Inspect pump unions and connections periodically for tightness—loose fittings on the suction side can draw air into the system during pump operation. Check the spa's water level regularly, as low water can allow air ingestion through skimmers.
After any service that opens the plumbing system, be prepared for potential air lock. Refilling and priming procedures become part of routine post-service startup. Understanding this expectation prevents frustration when service is followed by flow problems that are actually normal air lock requiring simple clearing rather than service failures requiring callbacks.
Multiple Pump Considerations
Spas with multiple pumps may develop air lock in one pump while others operate normally. Each pump may need individual air clearing through its own unions or bleed valves. The pump experiencing air lock may need water flow from other pumps to push air through the system—running the working pump while bleeding the problematic one sometimes helps.
Circulation pumps, being smaller and positioned differently than jet pumps, may clear differently. These continuous-duty pumps often prime more easily once the main plumbing contains water. If your circulation pump won't prime, focus first on clearing the main jet pumps, which often provides the flow that primes the circulation system subsequently.