When radiators go bad

Sometimes radiators leak between the sections. This one did. This is a rare look at the reason. The push nipple is rotted thin enough to crack in one place and have a hole in another. We plan on attempting to fix this one. We found a source of push nipples and we plan on replacing all the lower push nipples. The upper nipples all look to be in decent shape. Its the condensate that eats the nipples up eventually.