I live in Colorado and have no issue with nipples working here. This is the waterer and feeder that came with the coop I purchased.
I use an API 250D 200-Watt Pail and Birdbath De-icer with Guard and 6-Foot Cord to keep the water from freezing, so far so good.
The only issue I have is that the vertical nipple seems to freeze up in cold weather so I'm replacing it with a horizontal nipple. My understanding is they are less likely to freeze up... time will tell.
A Colorado breeder told me the nipple valves didn't work in their thinner atmosphere. That's good to know it's working for you. Let us know how the horizontal valves work for you.