How To Unfreeze Tankless Water Heater?

To unfreeze a tankless water heater, turn off the power supply and the water supply, and allow the heater to thaw naturally. Introduce a heat source, such as a hairdryer or space heater, to speed up the process if necessary.

In colder climates, insulating the pipes and keeping the heater in a warm area can prevent freezing. Additionally, regular maintenance, like draining and cleaning the unit, can help prevent future freezing issues. Remember to exercise caution when using heat sources and consult a professional if the problem persists.

How To Unfreeze Tankless Water Heater?


Understanding The Need To Unfreeze Your Tankless Water Heater

When the temperature drops, having hot water readily available becomes even more important. However, if you switch on your tankless water heater only to find that it’s frozen, it can quickly become a frustrating situation. Understanding why your tankless water heater is freezing, recognizing the signs of a frozen unit, and addressing the issue promptly is crucial to ensure you have a continuous supply of hot water throughout the winter months.

Why Is Your Tankless Water Heater Freezing?

Freezing of tankless water heaters can occur due to several reasons. Here are some common causes:

  • Insufficient insulation: If your tankless water heater is located in an inadequately insulated area, such as an unheated attic or basement, it becomes susceptible to freezing.
  • Low water flow: Tankless water heaters require a minimum flow rate to maintain warm water temperatures. Insufficient water flow through the unit can cause the pipes and heat exchanger to freeze.
  • Extreme cold weather: In regions with extreme temperatures, even a well-insulated tankless water heater can freeze, especially if it is exposed to prolonged sub-freezing conditions.

Signs Of A Frozen Tankless Water Heater

Recognizing the signs of a frozen tankless water heater can help you address the issue promptly. Look out for the following indicators:

  • Lack of hot water: The primary sign of a frozen tankless water heater is the absence of hot water when you turn on the faucet or shower.
  • Error codes: Some tankless water heaters have built-in error codes which display when the unit detects a frozen component or pipe. If you notice any error codes displayed on your unit, it could indicate a frozen water heater.
  • Strange noises: A frozen tankless water heater may produce unusual sounds such as banging, rattling, or hissing due to the expansion of frozen water within the system.

Importance Of Addressing A Frozen Tankless Water Heater Immediately

Dealing with a frozen tankless water heater promptly is essential to prevent further damage and ensure uninterrupted hot water supply. Here are a few reasons why addressing the issue immediately is crucial:

  • Prevents pipe bursts: Frozen water expands and exerts pressure on pipes, leading to potential bursts. By unfreezing the tankless water heater promptly, you can avoid costly repairs from pipe damage.
  • Protects the unit: Frozen components, such as heat exchangers or valves, can cause permanent damage to your tankless water heater if not addressed promptly.
  • Restores comfort: Having hot water readily available is essential, especially during the winter months. Resolving the frozen tankless water heater issue ensures a comfortable living environment.

Remember, if you’re unsure of how to unfreeze your tankless water heater or are hesitant to do so yourself, it’s always best to seek professional assistance to ensure a safe resolution.

Preparing To Unfreeze Your Tankless Water Heater

Ensuring Safety Precautions

Before attempting to unfreeze a tankless water heater, it’s important to prioritize safety precautions. Follow these guidelines to prevent any accidents or damage:

  • Turn off power: Locate the circuit breaker for the water heater and switch it off to avoid electrical hazards.
  • Shut off the gas supply: If your tankless water heater runs on gas, close the gas valve to prevent leaks or fire hazards.
  • Wear protective gear: Put on gloves and safety goggles to safeguard yourself from any chemicals or potential harm.
  • Allow sufficient ventilation: Ensure that the area around the water heater is well-ventilated to avoid the accumulation of harmful gases.

Gathering Necessary Tools And Materials

To effectively unfreeze your tankless water heater, gather these essential tools and materials beforehand:

  • Hairdryer or heat gun: A hairdryer or heat gun will help in thawing the frozen components gently.
  • Thermometer: Use a thermometer to measure the temperature of the water and monitor the progress of the unfreezing process.
  • Bucket or towels: Have a bucket or towels on hand to catch any water that may leak during the unfreezing.
  • Plumbing tools: Keep basic plumbing tools nearby, such as wrenches and pliers, in case you need to access any parts of the water heater.
  • Lubricant: Consider having a lubricant like wd-40 available for any frozen valves or joints that may require loosening.
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Shutting Off The Power And Water Supply

Before starting the unfreezing process, make sure to turn off the power and water supply to the tankless water heater. Here’s how:

  • Locate the circuit breaker for the water heater and switch it off to cut off the power supply.
  • Find the main shut-off valve for the water heater and close it to stop the water flow.
  • Open hot water faucets in your home to relieve any pressure within the system.
  • Identify any other valves connected to the water heater, such as isolation valves, and close them to further isolate the water supply.

By adhering to these safety precautions and ensuring the necessary tools and materials are readily available, you are now prepared to begin the process of unfreezing your tankless water heater. Remember to follow the specific steps for your particular model, as outlined by the manufacturer’s instructions, to avoid any additional complications.

Unfreezing Techniques For Your Tankless Water Heater

If you live in colder regions, you may encounter the frustrating problem of a frozen tankless water heater. When the temperatures drop below freezing, the water in the pipes can freeze, causing the heater to malfunction. In this section, we will discuss some effective techniques to unfreeze your tankless water heater and prevent future freezing.

Thawing The Frozen Pipes Using A Hairdryer:

Thawing the frozen pipes is the first step in unfreezing your tankless water heater. Here are some key points to keep in mind when using a hairdryer for this purpose:

  • Make sure the heater is turned off and unplugged before attempting to thaw the pipes.
  • Set your hairdryer to the lowest heat setting to prevent any damage to the pipes.
  • Start thawing the pipes from the faucet end and slowly work your way towards the heater.
  • Keep the hairdryer moving constantly to avoid overheating the pipes.

Applying Heat Tape To Prevent Future Freezing:

To prevent future freezing, you can apply heat tape to your tankless water heater pipes. Heat tape is an effective solution that keeps the pipes warm in low temperatures. Consider the following points when applying heat tape:

  • Choose heat tape that is specifically designed for water pipes and follow the manufacturer’s instructions for installation.
  • Wrap the heat tape around the pipes, ensuring that it covers the entire length.
  • Use electrical tape or zip ties to secure the heat tape in place.
  • Plug in the heat tape and adjust it to the appropriate temperature setting.

Flushing The System With Warm Water To Remove Ice Buildup:

To remove any ice buildup in your tankless water heater, flushing the system with warm water is crucial. Here are some important steps to follow when flushing the system:

  • Turn off the water supply to the heater and disconnect the power source.
  • Connect a hose to the drain valve and ensure the other end is in a safe draining area.
  • Open the drain valve and allow the water to drain fully from the heater.
  • Use warm water to flush the system by connecting a hose to the faucet end.
  • Turn on the hot water faucet and let the warm water flow through the heater for a few minutes.
  • Close the drain valve and reconnect the power source.

Remember, prevention is better than cure. Take necessary precautions to protect your tankless water heater from freezing. By implementing these unfreezing techniques and preventive measures, you can ensure that your tankless water heater functions efficiently even during extreme winter conditions.

Preventative Measures To Avoid Tankless Water Heater Freezing

Tankless water heaters are a reliable and efficient way to provide hot water in our homes. However, during the cold winter months, they can be prone to freezing, which can lead to expensive repairs and inconvenience. Fortunately, there are several preventative measures you can take to avoid tankless water heater freezing.

By following these tips, you can ensure that your water heater remains operational even in the coldest weather.

Insulating Exposed Pipes And Fittings

Proper insulation of exposed pipes and fittings is crucial in preventing tankless water heater freezing. Here are some key points to consider:

  • Insulate all accessible pipes and fittings with foam pipe insulation sleeves. This will provide an extra layer of protection against freezing temperatures.
  • Pay special attention to pipes and fittings located in unheated areas such as basements, attics, and crawl spaces. These areas are more susceptible to cold temperatures and need adequate insulation.
  • Make sure to seal any gaps or cracks in the insulation to prevent cold air from entering and affecting the pipes.
  • Insulate the water heater unit itself by using a water heater blanket or insulation kit. This will help maintain a stable temperature and prevent freezing.
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Maintaining Constant Water Flow During Cold Weather

Keeping a constant flow of water through your tankless water heater is essential in preventing freezing. Here’s what you need to know:

  • During extremely cold weather, it’s important to keep a small amount of water flowing through the heater at all times. This can be achieved by leaving a faucet slightly open. A slow trickle of water will help prevent freezing.
  • If you plan to be away from home for an extended period during cold weather, consider draining the water heater to prevent freezing. Consult the manufacturer’s instructions or seek professional help to ensure you do this correctly.
  • Regularly check for any leaks or dripping faucets throughout your plumbing system. Even a small leak can lead to water freezing in the pipes, causing potential damage.

Using A Thermostat-Controlled Bypass Valve

Another effective preventative measure is using a thermostat-controlled bypass valve. Consider the following:

  • A thermostat-controlled bypass valve allows a small amount of hot water to flow through the unit when freezing conditions are detected. This helps prevent the water inside the heater from freezing.
  • This valve is installed on the cold water line entering the tankless water heater and is equipped with a temperature sensor. When the sensor detects freezing temperatures, it automatically activates the bypass valve.
  • Consult with a professional plumber to determine if a thermostat-controlled bypass valve is compatible with your tankless water heater model and have it installed correctly.

By taking these preventative measures, you can avoid the hassle and expense of dealing with a frozen tankless water heater. Remember to insulate exposed pipes and fittings, maintain constant water flow, and consider using a thermostat-controlled bypass valve. Winter temperatures may be harsh, but with these precautions, your tankless water heater can withstand the freezing conditions and keep providing you with hot water when you need it the most.

Troubleshooting Common Issues After Unfreezing

So, you’ve successfully unfrozen your tankless water heater and now it’s time to ensure everything is back to normal. Here are a few key points to keep in mind when troubleshooting common issues after unfreezing:

Restoring Water Pressure And Flow

  • Check the water supply valve: Make sure the water supply valve is fully open to allow maximum water flow to the tankless water heater.
  • Remove any debris: If there is a decrease in water pressure, it could be due to debris clogging the water inlet screens or filters. Check for any obstructions and clean them if necessary.
  • Inspect the pressure relief valve: The pressure relief valve helps maintain proper pressure and should be in good working condition. Check for any leaks or signs of damage. If you notice any issues, it may need to be replaced.
  • Adjust temperature settings: Ensure that the temperature settings on the tankless water heater are set appropriately to prevent any issues with water pressure or flow.

Checking For Leaks Or Damaged Components

  • Inspect all connections: Carefully examine all the connections on the tankless water heater, including the water inlet and outlet, as well as the gas or electrical connections. Look for any leaks or signs of damage and address them promptly.
  • Check for water leakage: Keep a close eye on the surroundings of the tankless water heater and the pipes connected to it. Any water leakage could indicate a problem with the unit or the plumbing system.
  • Verify proper venting: Ensure that the venting system connected to the tankless water heater is in good condition. Look for any obstructions or damage that could impact the proper functioning of the unit.

Testing The Functionality Of The Tankless Water Heater

  • Turn on hot water taps: Open several hot water taps in your home to test the functionality of the tankless water heater. Check if the hot water is flowing efficiently and without any fluctuations in temperature.
  • Monitor water temperature: Keep an eye on the water temperature during usage. If there are frequent fluctuations or if the water is not reaching the desired temperature, there may be an issue with the unit that needs to be addressed.
  • Schedule regular maintenance: Tankless water heaters require regular maintenance to ensure optimal performance. It is recommended to have a professional inspect and service the unit annually to prevent any unexpected issues.
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Remember, it’s important to troubleshoot any problems promptly to prevent further damage and ensure a reliable supply of hot water. If you’re unsure or need additional assistance, don’t hesitate to contact a qualified professional for guidance.

Professional Help And Maintenance Tips

Having your tankless water heater freeze up can be a major inconvenience, but there are steps you can take to unfreeze it yourself. However, there are times when calling a professional plumber is necessary. Additionally, regular maintenance is crucial to prevent freezing in the future.

In this section, we will discuss when to call a professional plumber, scheduled maintenance for your tankless water heater, and some tips to prevent freezing in the future.

When To Call A Professional Plumber:

A frozen tankless water heater can be a tricky issue to handle on your own. Here are a few signs that indicate it’s time to seek professional help:

  • No hot water: If you’re not getting any hot water from your tankless water heater, it could be due to ice blockage or other technical issues that require expert assistance.
  • Water leaks: Frozen water inside the heater can cause cracks or leaks. If you notice any water leakage around your tankless water heater, it’s best to have a plumber assess the situation.
  • Strange noises: Unusual noises coming from your tankless water heater can signal a frozen component or other internal problems.

If you encounter any of these issues, reach out to a qualified plumber who specializes in tankless water heater repairs. They will have the necessary knowledge and tools to diagnose and resolve the problem effectively.

Scheduled Maintenance For Your Tankless Water Heater:

Prevention is better than cure, and this applies to your tankless water heater too. To avoid the inconvenience and cost of dealing with a frozen unit, make sure to perform regular maintenance. Here are some maintenance tips:

  • Flush the system annually: Over time, sediment can accumulate in your tankless water heater. Flushing the system annually removes sediment buildup and improves its performance.
  • Check for leaks: Inspect the unit regularly for any leaks or drips. Addressing minor leaks promptly can prevent larger issues down the line.
  • Insulate your pipes: Properly insulating the pipes connected to your tankless water heater can help protect them from freezing during cold weather.

By implementing these maintenance practices, you can extend the lifespan of your tankless water heater and reduce the risk of freezing and other problems.

Tips To Prevent Freezing In The Future:

Nobody wants to deal with a frozen tankless water heater more than once. Here are some additional tips to prevent freezing in the future:

  • Keep the area well-insulated: Make sure to insulate the area where your tankless water heater is installed. This includes walls, floors, and ceilings. Good insulation helps maintain a stable temperature and prevents freezing.
  • Install freeze protection devices: Consider installing freeze protection devices or heat tracing cables on exposed pipes. These devices can provide an added layer of protection during freezing temperatures.
  • Drain the system if unused: If you’re planning to be away from home for an extended period during the colder months, it’s wise to drain your tankless water heater system completely. This prevents water from sitting inside and freezing.

By following these preventive measures, you can minimize the risk of your tankless water heater freezing and ensure uninterrupted hot water supply throughout the year.

Remember, while some issues can be resolved on your own, it’s essential to recognize when professional assistance is necessary. Regular maintenance is key to keeping your tankless water heater in good working condition. By taking the right steps and being proactive, you can enjoy the benefits of hot water without the freeze-ups and headaches.


To unfreeze a tankless water heater, it is crucial to follow the proper steps and precautions. By addressing the issue promptly and employing effective thawing techniques, you can ensure the continuous functioning of your water heater. Firstly, disconnect the power supply to avoid any mishaps.

Then, inspect the exterior of the unit for any visible ice accumulation that could impede its performance. Next, use a heat source such as a hairdryer or heat gun to gently melt the ice, being cautious not to overheat the unit.

Once the ice is completely thawed, turn on the water supply and restore power to the heater. Regular maintenance, such as insulating pipes and ensuring proper ventilation, can prevent future freezing incidents. By following these steps, you can swiftly and safely resolve the issue of a frozen tankless water heater.


I am a mechanical engineer and love doing research on different home and outdoor heating options. When I am not working, I love spending time with my family and friends. I also enjoy blogging about my findings and helping others to find the best heating options for their needs.