It's 2 potential problems - the water freezing and the pipe itself freezing. Someone suggested PEX. Might be worth looking into?
What I mean about a nipple blowing out is that the pressure of the ice forces the metal bit out of its housing so that it pops out completely. That's irreparable.
A heater in a bucket will prevent this from happening to nipples that are attached to the bucket. They make what are called "Stock tank deicers" for this or you can buy heated waterers.