I'm guessing at the specs, but I think your filter's too small for your pump...or your pump's too big for your filter.

Assuming your pump's uprated (normal for AG pools) it's ballparking here, about the equivalent of a 1hp full-rated pump (normal for IG pools). And, a 1hp full-rated pump, like a Hayward Superpump, needs a 200# sand filter. One of our mods, Poconos (Al) goes for a 300# sand filter. That's because if you go over the filter's capacity, you have problems, but the performance improves the less of the capacity you use. So I run my pump on low speed and long ago noticed that my water gets clearer that way.

I'll let the pump pros confirm, deny, or refine my assessment.

BTW, what type of flexible plumbing do you have? If installed correctly, there's no reason to replace it. I use a combination of 1.5" hard PVC and 1.5" TigerFlex, which is flexible PVC that uses glued-on fittings just like the hard stuff. Al, at key points, actually uses automotive radiator hose, without any problem.

Carl