I'll take a first crack. No matter how much insulation you put around the AG pipes you will have to keep water flowing to keep them from freezing. All the insulation will do is slow the process. You have to consider the skimmer freezing as well. If you do consider just running the pump when temps dip below freezing, what about a power outage? That could be the achilles (sp) heel with your idea. To give you an idea of the severity of frost and freezing you could check the local building codes that deal with frost depths. Something tells me that in the Chicago area it will be deep enough to be concerned. Also remember that once you get an ice plug anywhere in the circulation system, you have no circulation. Personally I wouldn't take the chance. How about a much smaller and separate hot tub that would be more manageable?
Just some thoughts.
Al
BTW: I deleted the other thread.
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