This message serves as a warning to those that may wish to replace air vents on their hot water radiators. We just purchased a house and opted to replace all of the air vents as several had the original wooden handles broken off. We figured, while the plumber was at it, we could get all new vents. This turned out to be a mistake, as not one, but two radiators cracked at the air vent hole when the new std. pipe thread vents were screwed in! This cost us a lot of money, as we had to have the two radiators replaced, and they don’t even match the rest of the house. Now I have learned a lesson- if they aren’t broken, leave old radiators alone. They are more fargile than I ever imagined. Has anyone heard of anyone having a similar experience, or was this just bad luck?