So I just moved into a house with a pool and I'm trying to close it for the summer and as such, need to drain the water below the skimmer. I turned the jandy valve by my filter from the skimmer to what I thought was the main drain and started the pump up. It sucked water this way at a flow rate about half of what id see during normal filter running till the water level started dropping below the skimmer, then it stopped all together. Thinking maybe I was sucking water from the skimmer this whole time, I turned the jandy valve back to the original setting and watched where it sucked from. I saw it suck water from the skimmer so I set it back to the other setting and noticed it no longer sucked from the skimmer, so it must be the main drain except now its no longer sucking.
Anyone have any suggestions as to why my main drain stopped or what to do?
Also, I noticed a strange valve located after my jandy valve but before my filter pump. Any idea what this is for? For the life of me I cant figure out why it's there. See the attached picture of it.