I am helping my father in-law with leak detection. He says he's losing about 2-3 inches per night. In order to help him troubleshoot, I need to understand his plumbing. His pool has 1 return, 1 skimmer and one main drain. there is only a single line heading back to the filter (suction side) so I assume that the main drain is plumbed with the skimmer. Inside the skimmer there is a cover that can slide over the opening to the line going back to the pump. I assume this is used to control the amount of suction from the skimmer versus the main drain if it is partially There is also what looks to be like a valve on this assembly. It's like a plumbing ball valve perhaps. I assume this valve ****s off or turns on the main drain but I'm not sure.
If what I assume is true, I should be able to isolate the main drain, the skimmer and the single return to see if water drops when plugged.
My pool has separate lines for each skimmer and the main drain, so I've never seen this before. I'm looking to see if anyone can confirm this plumbing setup.