I bought 10 of those nipples awhile back. We finally figured out how to get them in the bucket. I guess we have stupid chickens because they have yet to figure out that there is water in those things. So I just use that bucket to huld water for their water bowl. It was a waste of money. And those that are on the PVC pipe must be a different type because there is no way to get the ones we got in such a small place. There are 2 parts to that nipple. One side goes in and the other is on the outside or bottom.
Lots of folks use nipples, and I think it does take a bit for them to learn how to use them. I think it only takes one smart chicken to figure it out and the rest of the flock will follow.
However, I bypassed that route, so I really don't know for sure. I purchased one of these: http://www.beaktime.com/2liter.php and I love it. It took about a week for my smarty Australorp to figure it out, and now they all get it, and use it so much I might get another one. I'm also trying to sew up some sort of insulating cozy that might keep it from freezing. Still working on that concept.....
^^^I'm a RidgeRunner, and will always feel best when surrounded by the PA mountains.^^^