People generally don’t want their hot tub to freeze. Keep the water heated and circulating with an insulated hot tub cover firmly in place and you shouldn’t have to worry about coming home to a mini ice rink.
Most hot tubs will not freeze overnight or even over a few days. There are hot tubs that can. These tend to be the hot tubs with external drains. It’s because of this we don’t use this type of drain.
Obviously, the design of the hot tub and quality of the insulation process, are important. You want to keep the water heated and circulating, so you need the spa to be energy efficient. And an insulated cover is very important.
The most likely cause of a hot tub freezing is loss of power.
If you lose power to your hot tub, the main thing is to not take the cover off multiple times. You will also want to avoid removing or opening the cabinet door unless you have to.
Additionally, you can buy yourself time, and maybe some peace of mind, by putting a 100-watt incandescent light bulb inside the cabinet. Alternatively, you might be able to fit a very small space heaters inside the cabinet. If so, turn it on a low-heat setting. You could keep the hot tub that way indefinitely. There is no repair that is urgent at that point.
Even with a Royal Spa hot tub, you should check on the hot tub weekly. Our spas are designed to run continuously. If you don’t have a Royal Spa or you’re going to be gone for months at a time, then you might choose to winterize your hot tub.