I have heated waterers, but this year I switched to buckets with nipples in the bottom. So I am going to try fish tank heaters in the buckets. But I am not sure if the nipple itself will freeze or not. So this year is up in the air. But I have the heated ones to fall back on if needed.
The nipples I use froze a few times last winter, and eventually started dripping/leaking after a 2 or 3 freeze-thaw cycles. Replacing the o-rings solved that easily. Mine are installed on pvc pipe, so I wondering if being in direct contact with warmer water will keep them from freezing. Clarkston has much colder winters that W. Wash. so may require something more.