If you live in an area with cold winters and have a need for an outdoor water bucket for a dog, you know that keeping it free of ice in the winter is a problem. I'd seen simple little heaters like this used in chicken coops, and decided to see if it would work to keep our dog's water bucket thawed. It worked perfectly, and didn't take more than 15 minutes to make.
It's just an 8" metal cookie tin wired with a light bulb inside, which serves as a heated base for the water bucket. A 40 watt bulb generates enough heat that it has kept our dog's 5 gallon bucket completely free of ice on nights that went into single digits, yet the surface of the tin never gets more than warm to the touch. On mild days in the 50s, even with the heater still on, the water stays cool.
You can see from the picture that a tin smaller than 8" diameter may be too small to fit everything inside. You'll also need the wire, plug, threaded pipe, nuts, and bulb socket which hardware stores usually sell as kits. I had an empty tin from Christmas and all the wiring gear except the socket on hand, so the whole thing only cost me $4. For added safety, cut the female end off a short length of grounded outdoor extension cord and use that instead of the lamp kit cord, which is likely not meant to be outdoors.
Drill a hole through the middle of the side wall of the tin the size of the lamp kit's threaded pipe (probably 3/8") and assemble the socket and wire through the hole, connecting the ground wire to the socket or tin.
Keep water out in case of spills or splashes with a dab of silicone sealant or anything else that will seal the gaps where water might be able to get in around the socket. The lid fits down over the bottom snugly enough that water isn't going to get in that way unless it got submerged. Even with that though, I'd want to keep this where it was reasonably well protected from the weather. Mine is on a covered patio, where blowing rain is the most it should ever get. Put the lid on the tin and set the dog's bucket on top.
If you want automatic operation and don't mind spending a little more, you can find a device called Easyheat that will turn on/off the electricity as needed.
The first night I used this, the bucket was frozen solid, so I brought it inside to thaw. When I took it back out to fill it, I didn't notice the ice had created two small leaks in the bottom. So for the next couple of hours it slowly emptied all over the heater. When I discovered the empty bucket, I checked the tin and it was still completely dry inside and the GFCI had not tripped. That helped convince me that it was adequately safe.
- Know what temperatures your dog can handle and bring them inside when it gets too cold. I'll assume you already have a doghouse for wind and rain shelter.
- Make sure that this is plugged into an outlet that has GFCI protection. It's been common for building codes to require exterior outlets be protected for at least 20 years, but don't assume yours are if you don't know for sure. Check it and don't run the risk of electrocuting your dog or yourself.
- If your dog chews, you'd want a chewproof cord or maybe protect it by running through a length of old hose.
- The cord in your lamp kit is likely not meant for outside so if you opt to use it, keep an eye on it to make sure it doesn't develop any breaks in the insulation from exposure to sun and cold. For extended use, it would be good to find outdoor rated cord or sacrifice a short outdoor extension cord to use instead.