it's got to be air... I'm bringing this pool back from the "ground up", just haven't done any excavation yet to reveal what I am sure is frost damage. There are minute bubbles evident in the strainer pot when running, although I don't know how to gauge how much is a lot. Cold starting the pump after it has been off for awhile seems to be fine, it seems to hold prime OK but maybe less than 100%. I'm thinking the break will be very close to the first 90s underground going back away from the pump, and my greatest suspicion is the main drain line. At this point I'm just happy to be running, and have my wife off my case. It's been an ordeal. For now, excellent flow and sparkling water, I love that DE filter.

40 x 20 x 12 inground concrete or gunnite
48000 gal
1-1/2" plumbing
est. 45 +/- years installed
new pump, filter, valve, chlorinator, all new "modern" electrical