Air bubbles in pool jets?

Do you see bubbles in the sight lid right before the pump? If your problem is on the suction side the bubbles would be there.If the leak was on the discharge one would think of losing water and having water weeping from the ground somewhere. I have a problem in one of my skimmer baskets returns and was able to find that out by having individual shutoffs for each inlet device coming from the pool. When i shut the one skimmer basket off the bubbles slowly disappeared from inside the basket with the sight lid. I have heard of taking a stethoscope and listening for leaks but have never tried it though.