Still a new pool owner that is learning every day..
I have a main drain in the bottom of my pool. It and the two skimmers each have separate pipe coming in to the pump.
My front skimmer pulls pretty hard.. My back skimmer (deep end) not so much. However, I have never felt any pull coming from the main drain. All three lines coming in have valves in the open position.
Is something wrong with my main drain? Should it always be pulling? If so, what steps should I take.