Sanger owner help

Hey there,
I have been lurking around here for a while and finally signed up and am posting. I am just curious if you could tell me how to winterize a Sanger 210? I am looking at buying an older 210 or a newer 215. I am going to water test this weekend and possibly purchase this weekend. However if I do I will have to re-winterize cause up here there is the possiblity of freezing again.

Thank you everyone
Dev

P.S. I did do a search and didn't find anything. if there is already a thread on this can you tell me what you used to search?