How To Thaw A Frozen Tankless Water Heater?

Hot water can be a necessity, especially in the cold winter months. Hot water heater tanks commonly freeze, but what about a tankless water heater? Interestingly enough, a tankless water heater does have the ability to freeze, leaving you without hot water. The good news is that there are several different ways to thaw and prevent this water heater from freezing.

Now, unless you are an avid outdoorsman, built for the snow and the cold, winter can be a pain. On the bright side, it does give us all an excuse to take a hot bath and relax with a cup of hot cocoa. Sounds lovely! Except for the fact that somehow your tankless water heater managed to freeze, leaving you just about as cold as the temperatures outside. While it may seem impossible now, hot water is in your near future.

What Causes A Tankless Water Heater To Freeze?

There are several different things that cause a tankless water heater to freeze, namely, cold weather. Most tankless water heaters come with some sort of insulation to prevent the unit from freezing; however, it is not impossible.

In most cases, there isn’t a need to worry about the water heater freezing because as long as the electricity and gas are working, the unit usually does not freeze. However, if a tree or heavy snowfall affects the power lines (or really anything that might get in the way), it’s a different story. Without a power supply through the water heater, it is prone to the elements and very likely to freeze.

Does Cold Weather Affect Tankless Water Heaters?

No, cold weather does not affect tankless water heaters. Most water heaters have built-in protection against freezing. This temporarily protects the tank from conditions ranging from -5 to -20 Fahrenheit.

Freezing Temperatures

How Do You Defrost A Frozen Water Heater?

Oh no, your water heater is completely frozen. First of all, that means it’s absolutely freezing outside, so our condolences. Second, you have no way to combat the icy weather, as your hot water isn’t desirable. We’re just as unhappy as you about forfeiting that cup of hot cocoa. Let’s take a look at how to defrost a frozen water heater.

First things first, make sure the unit is completely off. Turn off the electrical power and close the gas and water shutoff valves. To determine where to begin thawing your frozen water heater, first take a look at what section is frozen. Just to set expectations, in most cases, when the unit freezes, the pipes around it are also prone to freezing. Touch the water heater, as well as the pipes surrounding it. If there is frost on the pipes, it is definitely frozen.

Before you begin to thaw the heater, check for cracks or burst pipes. While it may sound strange, the heater often cannot house the expansion of the water when it freezes, which leads to bursting pipes. For any broken or burst pipes, contact your plumber.

To thaw the frozen section, use a blow dryer or space heater to thaw the unit evenly to thaw the frozen section. Though a blow torch may match your current mood, avoid using it, as the open flame is likely to cause problems. Apply the heat evenly to the frozen pipes; patience is critical.

Once you believe the pipes are sufficiently thawed and there are no visible cracks or bursts, you may turn the heater back on. If this does not fix the issue, turn the heater off again.

This can be a tedious process, and we want to let you know we’re remarkably proud of you for making it this far. If thawing the pipes did not restore the heater (in excessively cold climates, this is a possibility), detach the unit from the pipes. Take it somewhere where melting won’t ruin any carpet or décor, and place a space heater in the room. As the water heater warms up, any liquid previously in the unit will melt and probably make a mess.

Once thawed, return the heater to its desired unit, reconnect it, and turn the heater back on. Now, take a bow (even though no one is watching) and make that cup of hot cocoa; we know you deserve it.

How Do You Prevent A Tankless Water Heater From Freezing?

After completing the process of thawing the water heater, we would assume that’s not an experience you’d care to repeat. So, let’s take a look at how to make that something we don’t do again, and if we do, at least this time, we’re extra prepared.

Draining The Water Heater

When water stands still, the risk of freezing increases tenfold. One way to keep your water heater from freezing is to keep a steady stream of water running through the heater. Now, we certainly don’t mean turning the hot water faucet on full blast, but keeping a very slight stream of water trickling through it is a great way to combat freezing.


Insulation is arguably one of the most critical factors in keeping pipes and heaters from freezing. Heat tape and fiberglass are great for heating the unit itself. As for the piping, a heating cable or wrap insulation is a great protector.

Power Source

For the tankless water heaters’ built-in protection system to work, it must be connected to a power source or plugged in. If you often have power outages, consider a backup generator, or drain the water heater as soon as the power goes out.

Heater Placement

Although it sounds relatively simple, heater placement can be the difference between hot water and frozen water. Install the heater in a spot that has direct sunlight for the majority of the day or in an area that is heated. This will help prevent the heater from freezing and save a lot of headaches in the long run.

Recirculation System

A recirculation system is another option to consider; however, it is not entirely cost-effective. It is designed to move the water quickly to where it’s going without waiting for it to heat up. This system rapidly moves the water from the heater to whatever shower or faucet is turned on. The consistent water movement helps pipes not to freeze.

Routine Maintenance

Another important thing for any piece of equipment is routine maintenance. Due to the water heater being a particularly important piece of equipment, routinely checking on the pipes and the heater itself to determine if any frost or chills are developing is a great way to stay ahead of freezes.

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