Before you can begin to fix an air lock in a hot tub, you need to understand what it is. In most cases, an air lock occurs when you (or the home owner), drain the hot tub, clean it and then refill it. During the time that the hot tub sits without water, air can become trapped inside. This air can prevent the hot tub jets from functioning and even damage the tub tub if not repaired.
When an air lock happens, you will quickly notice the problem. When turning on the jets, you will hear the motor running but you will not see any water movement in the spa that there should be. That is because there is air trapped inside the plumbing, preventing the water from flowing normally.
HOW TO FIX
1. locate the water pump (usually located close to the spa pack under the skirt)
2. Find the large Union Nut connecting the plumbing to the pump. Using your hands or a pipe wrench, slowly loosen the nut until you hear the air coming out.
3. Once a small amount of water starts coming out of the union area the air will have been released and you can tighten the pump union back up.
4. Turn off the pump and then back on again to ensure that the issue has been resolved.