The way I think it works is if the basket were to get full to the point where it blocks flow then it'll pull from the second spot
That is what I think too but dang if I can understand how that would work and why it was done this particular way.
I can always choke off the skimmer basket and test that theory. I’ve got plenty of leaves. LOL!
I’ll do that another day and report back.
Best speculation is that this was done when the new liner was put in. Now why they’d do this instead of putting another hole under the skimmer is beyond me. Seems like a lot of plumbing work and the oddball location just screams former return jet at me.
It’s not the original skimmer and no telling when, why or how that was changed out so might have actually been an easy conversion plumbing wise if the lines all run under the decking (probably do).
Half of that whole side of the pool is a dead zone with no circulation. Everything collects in the corner. Be nice to have a return jet there.
I’ll still do some digging to at least try and find out what’s what. It’s good exercise too. You’re right though and I may well end up leaving it alone. We will see what I unearth.
Main drain cover looks new (at least not 1980’s) so I’m positive as can be that was replaced with the liner a couple years ago. I’m aware it’s not up to code. No small children here or that will be visiting so no worries there. If it traps anything else, well, I guess I didn’t clean the pool often enough.
Running the main drain at ~10% is the plan. Just enough to keep it flowing water.
Ordering SWG tomorrow and comparing pump curves for that final decision.
Any thoughts on cartridge filter beyond the biggest I can afford? Looking at one large filter media versus 4 or 5 smaller media, I’m leaning towards the multiple media. Any input there? Pros/cons of each?