I have three inlet valves (skimmer, main drain and cleaner). For as long as we’ve owned the pool we’ve only ever had the “skimmer” valve open. It’s the way it was when we got here and we’ve just never touched it. Question is - is there a good reason to also open the main drain valve? The cleaner valve has a cap on it in the side of the pool that only gets opened if we attach a vacuum, so that one doesn’t pull any water in, even if the valve is open.