They didn't leak or drip when the birds weren't drinking, the birds made a mess when using them. I'd watch them peck the nipples, and some got in the bird, some got on the bird, and some hit the ground.
I'm not a fan of the nipple system. Tried it this summer, hoping that it would provide a cleaner water system, and save water. Though, the water is cleaner, it turned the coop into a swamp right where they were drinking. Half of the water ends up in the bird, half on the ground. You need a good...