I have had both vertical and horizontal nipples. I live in an area where winters are below freezing. The vertical nipples can be a bit harder to protect from freezing, but they almost never got stuck and leaked.
Then I switched to horizontal nipples when the vertical nipples wore out. While being a bit easier to protect against freezing, these new nipples leak like crazy as the chickens' dirty beaks leave material on the nipples that get lodged in the seals, requiring frequent manipulation to clean them to stop the leaks.
Don't get me wrong. I adore nipple water systems due to having clean water for the chickens without needing to clean and refill them daily. Nipples are really the best way to go when deciding what water system you are going to have. But choose which kind will be kindest to you.
