I'm a big fan of unions anywhere there's a piece of equipment that you might want to remove. They're cheap & helpful.
*Unions into & out of the heater (might need to replace the heater),
*Unions into & out of the filter (might need to get into the filter - my multiport valve is at the top of my filter),
*Unions into & out of the pump,
*Unions on either side of valves.
I'm also no plumber or an expert on flow rates, so maybe there's a reason this isn't a good suggestion. Come up voice - I'm willing to learn.
Here's my short story on my pool guy "help" - I had many of those unions in place. When I replaced my filter DIY, I didn't re-plumb the heater back in (I'm not good at eyeballin' long PVC runs). I hired my pool guy to get the heater back into the loop and he took it on himself to "tidy up" the rest of the pad, cutting out most of those unions & replacing them w/ glued slip joints.
Here is a pad I renovated for a customer. Replumbed from the ground up.
Removed old pump and filter, installed an SD80 and Intelliflo VS pump.
Sorry if the pics are sideways, they are orientated correctly on my phone but won't upload that way.
[Merged from a similar new thread ... jblizzle]
Pentair Challenger 1.5hp pump/motor...Pentair TR-60 sand filter (new) with updated/improved push/pull backwash valve...and the Polaris booster pump. Jandy 2 way valves control two skimmers and the main drain. 3 way Jandy valve on the return line (fountain). I replumbed the backwash line to dump at the street/curb instead of the yard......oh, the inline chlorinator is no longer used since I joined the site..lol