From what I read, they have a lifetime warranty. I checked with them awhile ago, and they said if you remove the top half (a strap wrench should work), you can soak that part in vinegar for a few hours and it should clean it up and restore it. Might be a pain to do while in the heating season. Give them a call or drop them an e-mail...they seemed pretty responsive ad there may be some more info on their website. I think the working parts are limed up, and cleaning it should restore it. If not, then I don't know.