For the nearly 2 years I'd been brewing, my chilling method was the same: Cover the BK with foil, and let sit in my basement utility tub with 'ice bombs' until cool enough for pitching. Once I started AG, I did the same thing, but used the immersion chiller as well.
That area of my basement is not very sanitary-but I figured the foil would do the trick, and I made some good beers that way-so I figured things were fine. I did find it peculiar that it took the wort a long time to chill-most often it would take at least an hour.
Then I had a few sub-par batches. One was undrinkable, and another was not too bad, but I knew that I had some minor infection. I was pretty frustrated, and sought advice on here and among local brewers to figure out what it could be. After ruling out several possibilities, I figured that something was making its way in there while cooling. It made sense, given the fact that the wort would sit in a dingy tub for a decent amount of time.
Instead, I started hooking up the IC to a outside spigot. I realized that it was actually cooling much faster than I'd thought. The problem was that my floating thermometer was floating on the very top-in all the hottest wort-while the wort at the bottom of the BK was much cooler. When I swirled the wort around a bit-I was able to get the temp to pitching temp in 20 minutes or less. The shorter cooling time, and the fresh-air environment must have helped, because the three batches I've done this way have tasted great.
This was very encouraging, and has really renewed my confidence. It shows the evolutionary nature of brewing. Trial and error and refinement. In retrospect, I should have figured this out long ago...but sometimes it takes multiple screw-ups, and seeking advice, to get to the bottom of things. Not sure why I'm sharing-guess I just appreciate the help. Cheers!