Hi everyone. This is my first post, so forgive me if I forget to include some information. My husband and I have recently replaced our rabbits' water bottles with an automatic watering system with 5 gallon buckets and flex tubing. It has saved us a lot of time and frustration from constant refilling and leaky bottles. However, we are now facing freezing temperatures and having problems with keeping the water lines from freezing. We purchased submersible bucket water heaters and that has kept the bucket water from freezing, but not the lines. What would you suggest we use? Thanks for any input. Here are a couple of pictures of the system.