I think she meant horizontal, not vertical.
......and yes, no way cup would stay thawed with just heated water.
What is a V-nipple?
I had to edit. I meant to say horizontal nipple in my first post.
V-nipple is the vertical ones that hang down from the bucket.
AA - the photos you sent me in pm showed me how much more recessed the spring part is into the water. Then I ordered some and they are really way more into the bucket where the heat of the water in the bucket may keep them thawed so I'm hopeful.
Last winter it was in the negatives for several weeks. I just hate maintaining waterers. I do have a backup plan if this doesn't work but this option is safer (keeping the birds from frostbite compared to my other option) and I'm hoping these work and they learn to use them.