As soon as the thermometer reaches the frost line, the Arctic Cool should be disconnected from the water circuit and completely drained of water. Otherwise, frost damage will occur and water hoses in the device will become loose or burst if the water turns into ice and expands. But there are no problems for our pools, so nothing stands in the way of a nice ice bath even in frosty temperatures. I once captured it in a (unfortunately somewhat lengthy, I apologize for the lousy sound) hobby cell phone video. So, off to the deep end - and feel free to send us a higher quality video for the blog.