It’s such a common question we hear. People automatically assume there is a leak in their pool. They are usually right, but in a different way than they may think. In most cases it’s due to an air leak somewhere on the suction/vacuum side of the pool plumbing system. Air leaks usually don’t lead to any actual water loss in the pool, unless there is an underground plumbing leak on the suction side like on a skimmer or drain line. These leaks tend to lose water when the pump is off. Once off, when there is no longer a vacuum created on that line which would pull air into it through a leak, pool water is now allowed to escape back out of that line into the ground through the same leak.
Before looking for an air leak, first make sure your pool has an adequate water level. The normal operating level is about mid-way up the skimmer mouth. This level usually allows pool pump operation without the skimmer sucking air. Make sure that if there is a weir gate on the skimmer mouth that it floats freely, and doesn’t stick and block water from entering the skimmer. Next run water over and around the edges of the pump lid while the pump is primed and running. Watch and see if the air bubbles visible in the pump now disappear, when water is now drawn into the pump in place of air. Keep running the water over the pump and have someone watch the pool to see if the bubbles quit coming out of your pool returns, if so, you have likely solved the problem.
Usually the air leak can be found at or very near the pool pump. At least 50% are due to an old dried out or stretched pump lid gasket. When these get dried out and stiff, they can develop cracks which can allow air to enter when the pump runs. When over-stretched, they just don’t seal. Take the pump lid down to your favorite pool supply store and they can help you get the right gasket replacement. While you are there, purchase a small tube of pool grade lubricant to help keep the new gasket soft and allow for a better seal when the pump lid is tightened. Keep the areas under the pump lid and on top of the pump where the gasket rests clean. Also keep the lid gasket well lubed, but don’t use petroleum jelly, it can break down the rubber gasket.
Keeping the right water level in your pool, with the pump lid clean and well sealed, are the easiest and most common ways to fix an air leak on your own. There are several other places for you to look, too numerous to list now, which we will be discussing in future posts.