[jtroutma]

Invincible:

That setup sounds very close to my current setup. My pump is a bit different and I dont use an aluminum res..

Personally I would ditch the aluminum res. so you dont have to worry about corrosion. Get a plastic one or something simmilar.

As for the water possibly freezing, does your sink freeze up inside your house durring those cold times? As long as you have the system indoors and running, it shouldn't freeze over or at least not within say an hour. If you are really worried about it, then go with Cyco dudes suggestion about useing windshield wiper fluid; good cooling properties yet will not freeze at the same temps water will.