This was for a largish (40,000L) above-ground pool with no hookup to my home's plumbing system. The water was all pumped in from a water truck. The previous system was also installed by a non-professional and was mostly tubes. It leaked to all hell and looked generally redneck and awful.
First step was draining the pool and doing a nice deep clean. Then I ripped out all the original plumbing until it was just the pool outlets, pump, and filter.
I arranged it all and measured the dimensions. I fed the figures along with a tonne of photos and explanation to GPT. I spent a while talking pros/cons and landed on a design which lined up with what I'd seen on YouTube. I had it prepare me a full shopping list of PVC, tools, cements, etc. all linked to a local pool dealer. I picked it up the next day.
The PVC was all cut with a chop-saw then primed and cemented together. I found this part easier than I would have expected. I put a layer of TigerFlex hose between the PVC manifold and the pump/pool/filter inlets so it had some tolerance.
We've been swimming in it all summer, no issues whatsoever so far.