I filled the bucket to within 3" of the top with cold tap water, plugged the heater in, and set a timer. Here's the breakdown for heating a full 5-gallon pail:
- At 10 minutes, the water was lukewarm
- At 20 minutes, the water was hot and steaming--hotter than I would like for a bath, but not painful. I could keep my hand in it comfortably.
- At 30 minutes, the water was so hot that I could only dip my finger in for a second. At this point I unplugged the heater, although it will bring the water to boiling if you leave it in long enough.
I don't know if 5-gallon plastic buckets release chemicals when they're filled with hot water. Would a PETE (food-safe) bucket be safer than a regular one you can get at a home improvement store? I don't know, but it certainly wouldn't hurt to use one. You can ask for used frosting buckets at the cake decorating departments in grocery stores. Chinese restaurants often have 5-gallon food-safe pails, originally filled with soy sauce or vegetable oil.
It would be interesting to heat identical volumes of water on a stovetop and in a bucket heater and compare which is faster. If someone ever does that experiment, please let me know!