What kind of waterer do you have now? Do you have electric to the coop or can you run a heavy duty extension cord to it? I don't know how cold you really get, but a lot of people on here don't use heat in the coop and they get temps down below zero. Chickens keep warm, from all the down feathers that they have. Good ventilation is more important than heat.
I use a watering system similar to blackdog. Instead of the 5 gallon bucket I use a 10 gallon plastic tote with lid. That way the birds only need watered once a week. The water is kept outside in the run. No sense in adding any potential source of moisture inside the coop.
I'm not sure how cold it gets where you are, but it gets to -22 here and I have never heated the coop. Each chicken carries around its own down blanket. They actually do better in cold weather than in the heat of summer. My birds are outside all day in a covered run no matter how cold it gets. I do allow for plenty of ventilation up high in the coop where no breeze will blow on the birds. A dry chicken is a warm chicken. Getting the moisture from pooping and breathing out of the coop is important. If you heat the coop you will want to close it off to keep the heat in. This will allow moisture in the coop and will defeat your desire to keep your birds warm. I also use a 2 by 4 for roosts. That way the birds can sit on their own feet at night and keep their feet toasty warm.
Let me add more about heating a coop. Every winter we get people writing into the forums saying they wish they had never heated their coops. These people have all had coop firs and lost all or most of their birds. I am sure this winter will not be any different from other winters.