Hello to all. I have a question I have been wanting to ask for a few weeks. When we had our pool built, they installed a Y-line connection from our outside faucet to "somewhere" in the pool (all underground). I know they told us exactly what it is for and HOW it works during pool school, but for the life of me I cannot remember now. I take it, it is for some type of "auto-fill". Can the pros here explain how this works (please explain for dummies like me)? Thanks in advance.