Hi: Converted my Superpump 1hp to a 1hp 2 speed this spring... works great! My question is... why am I getting a bit of an air bubble in my pump basket when I run it on low speed? The air bubble seems to grow a little bit if I run it continuously for a day or so. Water seems to be moving fine, no air coming out of returns, and there is never any air in the pump basket when I run it on full speed. Just trying to figure out if there is some kind of problem here or not. Thanks.