I've got a ~32k gallon pool. The lines are smaller than what they should have been when the pool was built 25 years ago. I'm probably going to have the pool resurfaced in the next year and have a spillover spa that we'll probably have filled in and converted to a sun ledge. With a 1.5hpx1.1sf pump and a perfectly clean 60sqft DE filter (with a multiport), I'm pushing 65-70gpm.
On the suction side: 1.5" line from main drain, 1.5" line from 2 skimmers tied together, and 2" line from spa drain.
On the pressure side: 2" line to 5 or so return jets, 2" line to 3 spa jets, and a 1.25" line to 3 "whale hole" returns in the deep end (literally, 3 holes in the side wall of the pool, no eyes/jets/fittings).
These are just the sizes of the pipes as they come out at the pad; who knows what's going on for the lines that split for the jets, etc.
Each of the 6 lines has it's own valve at the equipment pad; partially closing any of the suction side lines drops my flow. On the pressure side, closing off the 1.25" line doesn't affect flow at all. Further, looking up IDs of PVC, my suction side has a total 7.42 sq.in. area and the pressure side has 8.2 (I'm guessing it's not quite as easy as adding cross-sections to find effective total pipe size but FWIW).
All of this tells me my suction side is obviously what's holding me back flow-wise. Here's where I'm going with this if you couldn't tell from the title: I'm debating repurposing pressure-side lines for suction lines. This doesn't need to coincide at all with the pool work, but that's what got me thinking about it (when we fill in the spa, we're going to keep the return jets and T the spa drain through the fill-in and out through the spa wall into the pool so we don't lose any precious line).
I'm thinking the pressure side could stand to lose the 1.25" line (feeding the whale holes)- and that those whale holes might be a better choice for suction than the pool or spa jets. I'd just re-plumb at the pad. That would change my net suction side to 8.9 sq. in. and net pressure side to 6.7. Repurposing a 2" line might be just too much (though I guess I could experiment and see which give the better flow).
Am I thinking straight here?
Thanks for reading!