So, as I said in this post my filter exploded. The most plausible explanation was that it was just its time. So, after looking around and asking for some feedback, I went with the Hayward 1750 (though the PS thought it was way too big and I should have done 1200 - but for an extra $80, I followed the TFP tenet of oversizing).
So, FiL and I did a pretty good job of plumbing it in. Probably took 3x-4x what PB would have taken, but whatever. And we're about to turn it on.... let me digress a moment: all that time, the new heat pump which was plumbed in last weekend (Sunrunner/Aquapro 1300) had been flashing "LP". Didn't think anything of it because there was no flow... in hindsight, the message for no flow should have been "FLO"; "LP" means either ambient temp is less than 60 (hardly, MIA was well over 80 today) or low refrigerant pressure.
Anyway, I turn on pump on, and there are no leaks in our piping. Job well done! Then we step back, and the output from the HP back to the pool is leaking and the area is oily to the touch.
What could have possibly caused loss of refrigerant.... and, could that have been the cause of whatever clog/pressure buildup that blew up my filter? The way I see it, whatever messed up the HP (which was running when the incident took place) and caused the loss of refrigerant blew out the pipes into the filter, cracked it, and messed up the output from the HP. Possible?
Of course, I would expect Leslie's to make good on fixing (even replacing) a 3-day old HP. The question would be: could I make some connection between that and the filter blow up? Granted, the filter was easily 10 years old and maybe on its last legs, but it had been working just fine until the HP got connected and LP came up.
The only thing Leslie's did not do was do the electrical, but if there was something wrong there, a breaker would have tripped or a fuse blown - not refrigerant going missing.
Meanwhile, pool is still sparkling clean. Even with the leak, I let the pump run for 2 hours just to get the water moving. Water still tested OK (FC 4 on a 60 CYA), so I did add plenty HOCl for another 2-3 days of no circulation. I did notice some cloudiness perhaps even oily sheen from the returns as it ran - is that normal on new cartridge, or is that refrigerant getting in the water?
As always, thanks in advance for comments/feedback.