Hi, we have a Intex Krystal Clear Sand Filter (12 inch) for our above ground pool. This is the 2nd season we have used it. Well, it works great for around an hour or so, and then the water flow going back into the pool completely loses pressure and barely any will come out. Once we backwash the pump, the pressure comes back for another hour or so. The water is crystal clear. Can anyone help!? Thanks! Kellie