Join the club, I've had bad chewers before. I put my buckets in a milk crate.
I run the cord out the bottom of the milk crate, lace it through the chain link
near the bottom so they can't pull it back through. Then the milk crate is secured to the chain link fence (which helps hide the bucket cord better).
It doesn't stop them from chewing on the lip of the bucket. Believe it or not but I have a bucket years old that the lip edge was eaten years ago and it still works. The rain/snow goes between the bucket sides and out the bottom.
Good Luck

Run the cord through a heavy pvc pipe and attach the pipe to a kennel panel going straight up, I run an extension cord along the top to get to the GFI making sure no dogs can reach it. We also build a wood box to go around the bucket so they can't get to the plastic. Works great. You can also use a big regular bucket and a submersible tank heater with the cord run through a pvc pipe, just make sure not to ever let the bucket run out of water and that its a GFI outdoor outlet to prevent shock if something were to go wrong. Hope that helps....