For several years I have had very slow water dispensing and hollow ice. I replaced the icemaker and that helped with making ice but it is still hollow. I have put in a bypass filter and that didn't help at all. So I now suspect a water valve. Can someone help me understand the difference in function between the primary and secondary water valves? that is my delima at the moment. I suppose water line and pressure could be an issue, but I doubt it. thanks