SS, the reason I asked about the Northstar, is that if the basket isn't in correctly, the lid won't completely seal - resulting in what you describe. I'm not 'up' on my Sta-rite pumps, but does your basket only go in one way (ie, there's a hole in it that matches up to the suction port) - If so, when the basket is slightly off center, it prevents the lid from being able to fully seal.