i'm a new pool owner so i don't know much about all this plumming and valves and stuff. i purchased a house with a pool and spa, i installed the pump and filter but no heater, will hopefully do that later on.everything seems to be working fine except one skimmer, the one at the shallow end does not suck any water. i tried adjusting the 3 port valve but the only one that chages is the one at the deep end. what can i do to troubleshoot this. i have 3 pipes coming from the ground that go into the 3 port valve and then to the pump. how can i make the skimmer work? is it necessary? i will try and post a pic to see if anybody can tell me what's going on