We are using a nipple watering system. 5 gallon bucket, raised on a platform on the outside of our coop with PVC with nipples running one line into the coop and one line into the run. It's been a great system for us thus far, but lately, the nipples are freezing up, even when we are barely approaching the freezing mark! The water in the bucket and the PVC isn't frozen - I check it twice a day. We have a bird bath heater in the bucket and heat wire wrapped around the PVC, but every morning, both the inside and outside nipples are frozen stiff. The temp in the coop isn't freezing so we just can't figure out why they keep sticking and locking up, seeming frozen. Any thoughts? Anyone else successfully used a nipple watering system through the winter? Bad nipples? Thanks!