It is important to use horizontal nipples rather than vertical nipples during winter. The horizontal nipples have a little O ring that keeps water out of the nipple when not in use. The vertical ones do not. That little bit of water in the vertical nipple can cause the nipple itself to freeze...
My waterer is kept outside in the run. It gets cold here in Montana. My water has never froze and it has gotten down to -22 F at least once a winter. I use a semi clear 11 gallon tote with lid, horizontal nipples, and a 250 watt stock tank deicer that is rated for use in plastic. The stock...