Been a problem, to varying degrees, for quite a few years - air bubbles coming out of the return lines. Particularly noticeable since opening the pool this year. Very weird stuff going on with my pressure though. Filter pressure psi is going DOWN instead of up - that's weird. And so, the pressure coming out of the return lines is really pretty significant right now - almost like when there are no grids in the tank. It's not blowing DE into the pool, it's all air bubbles. As I said, this is not a new situation and sometimes (with higher pressure on the gauge) there is no discernible air coming through at all as the amount of flow coming through the returns lessens - like especially right before the DE needs to be cleaned out and psi is way up. If I turn the diverter valve all the way to drain side instead of skim - the amount of air bubbles increases. So....a leak somewhere in the pressure-side plumbing? I don't usually see much air in the pump strainer, since otherwise that would moreso indicate suction side leakage. Any suggestions? It's no real big deal except that it puts so much excess foam into the pool.