I was wondering if the main drain is supposed to be attached to the skimmer or can each be isolated and ran back to the pump on their own with their own control valve. I live in a cold climate where it freezes so I was thinking it would be best to have an isolated main drain as well as the skimmer isolated for winterizing purposes. I have seen most pool builders attach the main drain from the pool to the skimmer, but what it best especially in cold climates. Any thoughts?