I just tried to open our pool for the year, and the pump simply will not fully prime. It pulls water, and air and water spits out of the returns, but no prime. If anything, the pool is overfull, so that is not the issue. I have checked the pump basket seal, and it appears to be seated correctly. I am imagining that I have a leak on the suction side, but I cannot think of what it would be. There are no valves on that side. One union and that's it. Any help is greatly appreciated.