Just a quick followup to my clogged vacuum-line problem.
Since my main drain line was not clogged (just the pool-vac line), I switched the jandy valve fully to the main drain line, so the vacuum line was totally shut off. I noticed, even after thoroughly backflushing my sand filter, that the pressure seemed a few pounds low (read at the gauge on the top of the filter). Since I had replaced the pump impeller a year ago, I suspected there was something going on in there that wasn't good, so I took apart the pump and had a look. It turns out there were a number of palm seeds (small, hard, 1/4"-diameter spherical seeds) jammed in the impeller vanes. I cleaned out everything that I could, and then used a small thin screwdriver to remove all of the seeds. After putting everything back together, I gained back the 2-3 pounds of pressure that was missing.
Then I removed the pool creature's hose from the pool, propped open the vacuum line outlet cover (in the pool), and switched the jandy valve to 100% vacuum (main drain line completely shut off, in other words). Turned the pump back on, and still not much suction, but I heard a big "gurgle" in one of the pipes that I didn't expect.
After shutting off the pump, I started the process of using the Drain King. I first took all the screws out of the top of the jandy valve and removed it (to expose the vacuum line's pipe). I immediately noticed a small strand of fan-palm tree debris hanging out, and on further inspection with a flashlight, I could see a large snarled mess of this palm-tree stuff stuck at a 90-degree bend in the vacuum line pipe (right before it went into the ground). I have a claw-type "grabber" device that is used for picking small parts (screws, etc.) out of tiny crevices. It's about 30" long, so I used it to grab hold of the big snarled clog that was at the 90-degree bend in the vacuum line. I managed, after several tries, to get a good hold on it, and extracted the whole thing. Put the jandy valve back together, et voila, LOTS of vacuum suction! Problem solved.
So I never even got the opportunity to try the Drain King. I suspect it would have worked, however, because the clog was jammed up at a 90-degree bend in the pipe, and I would have used the Drain King to push the clog _backwards_ through the line and back into the pool.
Whew, I hope this long diatribe is comprehensible. Let me know if you have any questions or need further clarification.