A hot tub is a significant investment, and the last thing you want is a block of ice in your backyard if you should lose power during the winter. First of all, don’t panic. Most hot tubs can go 3-5 days without power in sub-zero temperatures. Here are some tips to help you survive a prolonged power outage.
Here are a few Do not's
Do Not Take off the Cover. Like your refrigerator during a power outage, you want to keep the cold in. Your hot tub is the same way. You want to keep the Heat IN.
Make sure your cover is on tight. If you experience high wind in your area, you might want to invest in wind straps. These go entirely over your cover from side to side.
I prefer straps that attach to the bottom of the skirt. If you use a style that attaches directly to the skirt and if the wind tears it off, you will likely damage it.
Do not Drain your hot tub. If you drain your hot tub, you are putting the plumbing at risk. Unless you can power up a shop vac, any remaining water in the bottom of the hot tub, the plumbing lines, and equipment will freeze. The likely damage to the hot tub will put it beyond economical repair.
Here are some DO's that can delay temperature loss.
If you know bad weather is coming. Turn up the temperature of your hot tub as high as it will go. This will buy you a little more time until your power comes back. Check if your hot tub has an extended temperature setting beyond the standard high of 104 degrees.
Wrap the equipment compartment. Even the best insulated hot tub has an Achilles Heel. Most equipment compartments let heat escape to prevent the pump from overheating. Conversely, it will also let cold air in. The best way to protect this area from freezing is to use old blankets or towels and wrap them around the pumps and heater. Caution be sure to turn the hot tub breaker off. You don’t want the power coming back on and causing a fire.
Invest in a thermal blanket. This is the same as a solar cover that you would put on a swimming pool.
You probably won’t find one already cut to the size and shape of your hot tub. These are relatively easy to cut and will add an extra layer to prevent heat loss.
Hot Water. If your power outage is going to be longer than 3-5 days, you may consider draining half the water after the water has gotten cold. Then replace it with hot water. Do not allow hot water to come in contact with the exposed shell, as it will probably be cold and can cause shell damage.
Antifreeze. Most pool, hardware, and boat stores carry a non-toxic antifreeze. Pour what would be equal to 10% of your water volume into your tub and try to mix the water manually. This is not my favorite method, as you must drain the hot tub and refill it after the power comes back.
If you have a generator. Here are some additional Tips
Please use caution and common sense when using any of these suggestions. Do not attempt if you are not sure what you are doing.
Generator connection. Some hot tubs have two breakers at the sub-panel. One runs the jet pumps. The other runs the heater and a circulation pump. A qualified electrician can add a 110v heater circuit to your generator system. This is only recommended for hot tubs that have this feature. I would only recommend this for a whole-house generator system. Do not attempt to run the entire hot tub on a generator unless stated in your owner’s manual or by the manufacturer.
Heat. You can use a Small ceramic heater or incandescent trouble light to keep the equipment compartment warm. Click to see this video on placement.
Submersible Pump. Purchase a small submersible pump, place it at the bottom of your hot tub and run it 24/7. Moving water takes longer to freeze. The friction of the water moving through the pump will also add a small amount of heat.
One last thought. If you have the time and enough warning of a potential storm, drain and winterize your hot tub. I put this last as it is a lot of work to attempt in such cold conditions. You could use the water for the backyard ice rink you always wanted.