What is this gate valve for. I'm trying to close/eliminate drain suction and only have suction from the skimmer. I don't want suction from the drain. I though this gate valve controls the percentage between skimmer and drain. I'm not the original owner of the pool, so i'm trying to understand how this works. The drain is deep in the pool so i can't tell if it has suction or not, but i thought but turning the gate valve either way i can check if the skimmer suction gets turned off, but nothing seem to be affected.