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How To Prevent Your Tankless Water Heater From Freezing

Local Domestic Heating System Installed In Bathroom, Middle Capacity Boiler, Wall Mounted

Tankless water heaters are becoming popular among homeowners due to several reasons. They are environmentally friendly, energy-saving, and more efficient. Forget about standing for hours to get hot water, as with the help of tankless water heaters; you can have it within a few seconds.

But what about when the tankless water heater freezes in colder weather?

Don’t worry if that is the case! There are several precautions you can take to keep it working well. But how?


The most basic preventive measure to keep your tankless water heater from freezing is to place it in an insulated place. Mounting your heater in a sheltered and insulated place will keep it working for longer.

If you have installed it in a warm place, still facing the issue, here are some other ways that can be helpful.

  • Insulate the pipes.
  • Run water through the heater.
  • Maintain power source.
  • Drain the water heater.

Read further to learn the preventive ways to keep your tankless water heater from freezing.

7 Ways To Prevent Your Tankless Water Heater From Freezing

The chilly weather calls for hot water, but the most terrible thing is not getting it due to a frozen water heater. Nobody wants to use colder water in extreme weather, so you must take preventive measures to keep it from getting frozen.

Furthermore, once the heater is frozen, it expands, damaging other crucial components of the appliance.

Here are a few ways to keep it from freezing.

1. Install the Heater in a Warm Place

Worker Set Up Electric Heating Boiler At Home.

If you have a sheltered outdoor space, use it for installing your tankless water heater. You can also place a protective fence around the appliance to stop the strong winds.

The attic or basement can also be ideal for the heater to keep it sheltered from harsh weather.

2. Maintain a Power Source

Wall Hung Gas Boiler And Electric Water Heater

Your tankless water heater has a higher chance of freezing if it is out of power for a long time. This is because you must keep it plugged in all the time during chilly weather. Furthermore, you also need backup power sources like a generator or battery backup in case of a power outage.

The inbuilt freezing system in your heater kicks in once the temperature drops between -5 to -22 Fahrenheit, which protects your appliance from freezing. However, it also requires a constant power source for working. The built-in system will also stop working if you run out of power.

3. Drain the Water Heater

Water Heater In Bathroom.

You might not realize, but a small amount of water can accumulate in your heater that can freeze in harsh weather. Therefore, it is recommended to empty the heater if you are not using it for any reason, such as:

  • During power outages.
  • When going away from home during winter.

The heaters have a solenoid valve as freezing protection that opens once your heater is powered off and closes once it is powered on. You can drain the water from the heater using these valves.

It is a crucial step for the safety of your appliance, as frozen heaters and pipes can get cracked, resulting in irreplaceable damage.

4. Insulating the Pipes

Pipe Insulation Cutting And Mounting

One of the common mistakes that freezes your tankless water heater is neglecting the pipes attached to it. Keep in mind that heaters have an inbuilt freezing system, but it doesn’t work on the pipes, and you must also protect them from harsh weather.

If you are going away for a while, it is advisable to drain the pipes and insulate them using heat tape, polyethylene insulation, or fiberglass. It will keep your pipes well protected from the cold weather and also help in getting hot water much quicker.

You can also insulate your heater by using an insulation blanket. It will keep the heater well-protected even in extreme weather.

5. Seal the Direct Vent Heater Joints

Air Ventilation Moisture Duct In Bathroom Pipe Hole At Ceiling.

Tankless water heaters mainly have two types:

  • Direct vent.
  • Non-direct vent.

The direct vent is an older type that takes air from the room it is installed in and uses it for combustion. In comparison, the other type of non-direct vent takes air from outside. You will notice several joints around the appliance in a direct vent heater. It is advisable to seal them using tape as in harsh weather, the room air tends to get colder and can freeze the heater.

For non-direct heaters, ensure your pipes are well insulated and sealed to prevent exposure to outside weather.

6. Run Water Through the Heater

Hand Of A Young Women Setting The Temperature Of The Electric Water Heater.

As mentioned earlier, the small amount of water left inside the heater can freeze; the only way to prevent it is if the water keeps running instead of standing still. The best thing is to open a faucet far from the heater and let a tiny stream of water flows through the pipes. It will keep things moving, and your water won’t freeze.

We understand it sounds like an impractical solution with a higher water bill, but it is good if you feel your heater is vulnerable and there is extreme weather to deal with.

Instead of wasting the water, use a bucket to collect it for later use. Usually, the inbuilt freezing system is ample for keeping the heater from freezing, but if you notice things are getting out of hand, try this method as well.

7. Install a Recirculation System

Stationary Device For Forced Ventilation Of Air In An Office Or Apartment, Selective Focus

A recirculation system is used to get an instant hot water supply to a specific area of your home. Moreover, it keeps the pipes warm and prevents plumbing lines from freezing.

It does sound like a good idea, but an expensive one. The installation cost of a recirculation system is not worth it if you only require it to prevent your heater from freezing.

However, if you also have other needs for the system, opting for it can be beneficial to keep the water from freezing even in harsh weather.


Tankless water heaters are a blessing in colder weather as it provides hot water within no time. In addition, it is easy to maintain and use; however, you must pay closer attention to it during harsh weather.

Insulate the pipes or check the already insulated ones for wear and tear. Make sure to drain the heater and pipes if you are going away. It is also good to keep a power backup to keep your heater from freezing during extreme weather.

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