Thanks for the confirmation John...I thought that might be asking for trouble. I'll just drain the loop. I found a real easy way to drain my loop in literally 5 seconds.
Just insert a trumpet/cornet mouthpiece into the end of the loop and blow! All liquid goes back through the pump into the reservoir. It's a little hard blowing back through 3 blocks, but nothing a healthy person couldn't manage. Now I know why the flow is just a dribble even using a 1000+ gph pump. Not only does the extreme cold liquid make it sluggish, but the resistance of the blocks is much greater than I ever thought. Anyway, even if you don't play, you can pick up a trumpet mouthpiece for $25 or under at any music store or on ebay.