I have a new pool and lately I have noticed a small amount of air coming into the filler basket through the front pipe via bubbles when the pump turns off, enough where it slowly drains the basket after a couple of hours. I don't notice any water around joints coming out of pipes or a drop in water level of the pool. The lid is fastened like it should be, but you can here air bubbling in the pipes before filler basket if you put your ear on it. Sometimes it doesn't start this air leak for an hour or so after pump is off. What could be causing this? Does this sound like something above ground?

Does it only happen when the pump is off? If the pump and equipment are higher in elevation than the pool, water can slowly run back to the pool. While the pump is running suction helps keep the lid sealed on the pump, when the pump is turned off it is possible that the lack of suction could result in a small air leak allowing water to drain back to the pool.

It could also be cavatation. If your pump HP is too much for the plumbing, or if the plumbing has an abundance of 90 degree fittings. The water will acually swirl through the piping and create air at the 90 and bring it into the pump. Do you loose water? If so you could have a suction side leak. Check the fittings at the front of the pump for tightness, if it is a union check the oring for problems. I hope this helps a little.