Thanks to all who posted to this thread.
I plumbed in an intelliflo a few days ago. I was shocked at the amount of air in the basket, and after fiddling with unions and 90s and O rings, etc, I was pretty ticked off. At high speeds the basket had about an inch of air in the top, it looked like a pot of water on the kitchen stove at a fine rolling boil, waiting for the pasta to be added. At low speeds, the pot would drain down to the top of the pump intake level, with 4 inches of air in the basket.
Did soap suds. Nothing.
Did shaving cream. Nothing.
Then asked me wife for a small mirror and with mirror in hand I repeated the shaving cream. It took about 50 seconds for a pinhole to form in about a 3/8" deep ring of shaving cream on a 3-way valve right before the pump. And of course, the pinhole was on the bottom. Even laying on the ground with my ear pressed to earth I couldn't see it. Only with the mirror.
Okay, so I have this "micro pinhole", but surely there has to be another leak somewhere. After all the amount of air getting into the basket certainly seemed significant. I looked, I unthreaded, inspected, and rethreraded the pump unions, etc, etc. Nothing.
I was leaving town the next morning. I had just opened the pool and needed to shock the **** out of it, and I wanted the pump to be running for the couple of days I was going to be gone. For grins I took an old tube of caulk and placed a thin smear of caulk around the union with the pinhole. The air in the pump basket disappeared. Ridiculous. Ran several PRM changes with the pump. No air bubbles. Unreal. That one pinhole, and I mean a very tiny pinhole, was actually responsible for all that air.
the caulk slowly got sicked in I added more and more, then shut the pump down for an hour. The pump basket stayed full. No gurgling. Then fired the pump up. It stayed primed, Ran through an RPM run. No bubbles at any RPM.
As much as I'd like to leave my caulk "repair" as is and simply pretend that all is well, I can't. I'm going to cut out the valve and replace it. I'll get to that next week after I source a new 3-way valve and pick up the needed pvc fittings.
Anyhow, I'm posting to to say "Thanks." I appreciate the info you all provide and the knowledge that you all share.
FWIW, when the installers plumbed my equipment pad way back in the yonder days, they left little to no "free pipe" between fittings and valves. The fittings and valves are literally adjacent to one another in several areas. So to replumb one section, I'd have had to of replumbed pretty much the whole shebang. I used a 2" Pipe Hog to try to minimize the amount of work I had to cut and replace. The pipe hog worked fine on the regular PVC fittings, but it chattered some when drilling out the 3-way valve body. It's that chattering that probably left a score line that resulted in the formation of the pinhole leak.