While extremely rare, it's actually not impossible for a water heater to freeze. The leading concern is that any standing water inside the tank or tankless unit will freeze and expand, permanently damaging the appliance at the same time.
If the issue is isolated to the water heater, turn off the power. Next, turn off the gas and water shutoff valves and disconnect the unit. Relocate it to a warm room or use a space heater if you can't move the water heater away from a chilly area. Once the unit starts warming up, the ice should melt.
Do NOT turn the water off unless there's an actual leak. The correct thing to do is to run the water 24/7 until temperatures rise.
There are a few situations where draining your water heater is a good precaution to ensure the unit can't freeze, such as if your power ever goes out during the winter when the outside temperature is below freezing.
Frozen hot water heater lines pose a similar problem as your other plumbing. To determine which lines are frozen, turn on the hot water at all your faucets. If some work, you have an isolated frozen hot water pipe. If none of them produce warm water, you likely have a frozen hot water heater line.
Pipes typically burst when exposed to extremely low temperatures for an extended period of time (anywhere from 1-3 days depending on temperature). This is especially true for pipes located on exterior walls. A frozen pipe is likely to burst when any water or liquid trapped within it freezes and begins to expand.
A large number of tankless water heaters have built-in freeze protection that works in temperatures down to -22 degrees F.
It also is recommended to turn on both hot and cold faucets near outside walls to allow a small trickle of water to run during the night and, if not used often, during extremely cold days as well.
Well, water heaters are designed to heat water, and when there's no water, the system works harder to do its job. If left on, it'll try to heat an empty tank. That leads to “dry firing,” where the heating element burns out, or worse, damages the tank itself.
In most instances, pouring hot water down the drain will unfreeze drain pipes. However, it's essential to take your time with this method to increase its effectiveness and ensure your safety. Follow these simple steps: Fill a pot with a half-gallon of water and bring it to a boil on the stove.
Your pipes will eventually begin to thaw on their own once the temperatures rise above freezing.
Before you start draining the tank, you'll want to shut off the cold water supply. The supply valve connects your water heater with the main water line. Unless you have access to a well (and you may need to drain the tank more regularly if you do), the water main delivers all the potable water your home uses.
Frozen pipes can cut off your home's water supply and cause damaging leaks. In many cases, the help of a plumber is needed to resolve the problem. To prevent further damage, it is generally recommended that you turn off your main water supply valve and your water heater until repairs have been made.
To defrost your HVAC unit, you want to begin by turning off your thermostat and turning your fan on. Let the fan run over the next few hours to allow your unit to defrost. After the unit is no longer visually frozen, you can try turning on the cool air to see if it is cooler than the temperature in your house.
If you don't want your water to freeze during winter, make sure to insulate your tank properly. A good way to do this is by using an insulating material that covers the tank on all sides including the top. This will prevent heat from escaping and keep the tank warm enough so that it doesn't freeze.
If you suspect your water heater may be frozen, touch the outside of the unit with your hand until you locate a spot where it's ice cold. If you don't find such a spot on the tank or tankless unit, you may have ice in the pipes leading in and out of the unit rather than in the heater itself.
Any water heater can freeze if water is left inside it
Tank water heaters usually hold between 40 and 55 gallons and can require electricity. So when the power goes out in freezing temperatures, the water eventually can freeze, expand and burst the storage tank.
Your pipes will eventually thaw on their own, but this will take at least a few hours or potentially several days, depending on where the pipe is located and the air temperature around it.
120 degrees Fahrenheit is the safety recommendation against scalding, but 140° is the common default setting. Most experts agree that anything below 120 degrees creates a risk for bacteria to develop inside your water heater from stagnant water, such as legionella that causes Legionnaire's disease.
Prevent Frozen Pipes
Moving water keeps pipes from freezing. Find shut off valves for emergencies. Insulate pipes in unheated areas. Open cupboards and vanities to warm pipes.
An open faucet that produces no water or only a slow trickle is a good reason to suspect that a pipe has frozen.
Keep the faucet open. As you treat the frozen pipe and the frozen area begins to melt, water will begin to flow through the frozen area. Running water through the pipe will help melt ice in the pipe.