How to Fix a Hot Tub Air Lock

An air lock occurs when air gets stuck in the plumbing lines of your hot tub. While this may not sound terrible in itself, air in your spa’s lines can cause significant damage over time if it is ignored. Here’s how to avoid and address an air lock issue.

Air Lock Prevention

Your hot tub’s pump is designed to pump water, not air. Air in the plumbing lines will prevent water circulation and could quickly destroy the pump itself.

Filling the Tub

When filling your hot tub, place the garden hose in the empty filter canister rather than in the actual tub. Once the water is on, this position fills the pumps and internal plumbing with water. Ultimately, this decreases the chance of an air lock in the pump once the power is on.

Bleeding the Pump

Once the hot tub is full, and before you turn on the power, “bleed” the pump to further reduce the risk of air:

  1. Turn the ground fault circuit interrupter (GFCI) off manually.
  2. Use a flat head screwdriver to turn the bleed valve (on the base of the pump) counter-clockwise.
  3. Keep the valve open until water trickles from the pump.
  4. Turn the bleed valve clockwise to tighten once the water trickles.

Never over-tighten the bleed valve or use a tool to turn it. That much force could break the thumb screw.

Priming Mode

Whenever the GFCI is turned on, your hot tub will start up in priming mode to safely remove any air that may be trapped in the plumbing lines. The spa will stay in priming mode for about six minutes. The heater is disabled during priming to prevent overheating and system damage.

Run Pumps to Purge Air

If you see an icon similar to the one above on your topside controls, push the pump button (starting with low speed then pushing again for high speed) to confirm that water is coming from all jets. All jets should send out water within two minutes.

Air Lock Repair

Fortunately, the signs of an air lock are quite noticeable, and the steps to remove the air lock are simple and quick. However, if you miss the signs or ignore them, the damage to your hot tub could be significant.

Here are the three main symptoms of an air lock in your spa plumbing lines:

  • Humming sound.
  • The pump (or pumps) isn’t working.
  • Some or all of the jets are not working.

In each of these cases, bleed the pump by following the steps above.

If your hot tub is suddenly experiencing low heat or no heat, you may have an air lock or closed slice valve. First ensure the slice valves are open, and then take steps to remove an air lock.

Additional Priming

When you run the pumps to purge air (see image of icon above), be prepared to turn the pump off and try a second priming session when the water has gone still. You’ll need to do this if jets aren’t working or if the water surges.

If the pumps don’t properly prime within two minutes on the second attempt, turn off the GFCI. Ensure that:

  • Slice valves are locked in the up positions.
  • Diverter valves are centered for even water distribution.
  • Jets without flow are truly rotated into the open position.
  • Filter and suction drain covers are free of debris.

Turn on the GFCI and repeat the priming mode with pumps on high speed when you see the priming mode icon your topside controls.

If this third attempt fails, contact the manufacturer for assistance. Never turn on a pump that won’t prime. If priming mode is allowed to complete on an improperly primed pump, the heater will automatically engage, possibly overheat and cause serious damage.

Air locks are easily prevented when all instructions are followed, and simply fixed if you know the signs. Pay close attention to potential air locks to avoid serious damage to your hot tub.

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