The answer is probably yes, but read on:
My pool is now almost a year old and it's working fine. It was an owner-builder endeavor that went pretty well, but I've never been completely satisfied with the plumbing. The guy I hired to do the work wasn't great and it was clear his knowledge was limited to a small pool template. For those of you that have a pool-vac working off your filter pump you'll know that there is a balance between sucking from your skimmer/drain and sucking from the vacuum line. That sweet spot was pretty complicated for me to find and I solved the problem through automation (you'll see in the pic below), finding the right RPMs on my VS pump, and managing the flow on the 2nd skimmers valve gate. It works fine, but I'm thinking that I could increase the tolerances and improve efficiency overall by replacing some 2" valves and related piping with 2.5" or 3".
In the picture you'll see that I have 4 lines on the suction side coming from my pool, and they all route through the filter pump:
1. The Spa drain.
2. The 1st skimmer and main pool drain. I've installed an actuator to close this valve when the vacuum turns on.
3. The Vacuum
4. The 2nd skimmer and another drain that is used to power a waterfall booster pump (just to the right)
You'll see at the pad that I have 2.5" pipes coming from both pool drains (2 & 4) and a 2" pipe for the vacuum. They all scale into the 2" ID portion of each jandy valve and head towards my VS pump as 2". On the return side of the pump it starts as 2" and heads all the way back to the pool. It eventually scales down to 1.5" pipe supporting 4 inlets that each have 3/4 openings. I've always wondered if I replaced the manifold (the top section of 1,2,3,4) with 2.5" or 3" pipe all the way to the pump that I may see better performance. I'd be able to push more water through the system and allow for a bit more flexibility when tweaking the vacuum. It's worth mentioning that when my pump is running at 2750 my Jandy cartridge filter only sees about 10psi. Also, from reading this forum and looking at my actual pump manual I don't think the 2" in and 2" out config for this pump is recommended. At above 2750RPMs I do start to see some cavitation.
Anyway, it's pushing winter here in SoCal and now is a good time to start messing with my pool. So... am I crazy to spend the 300 or so on parts, or do you think I may see some benefit? Thanks for your opinions and sorry for the long post!