I max my pump RPM in SPA mode which increases the pressure. Depending on the number of jet,s it would be normal to see the restriction cause a rise in pressure.
Even with near perfect chemistry, I have white build up on the tile surface. It takes muriatic acid and a pumice stone to remove. I do this twice a year.
My Warrior SI worked for one day. After that it would only run for 5 minutes at a time. Marina sent a return label and a new Warrior is on the way. I hope this one does not have the same problem.
2" would work, but I would insist on 2.5" for all three. There is a trend on this site recommending no main drain. I like being able to balance the waterflow. My water at 9' deep is cooler than the 92 degrees it is on the surface.
Same problem here. Even with a new gasket on the diverter, it still leaks. I'm about to switch to a cartridge, but for now I put a pipe plug in the back wash line. I take it out when I need to backwash.