How to Fix Tankless Water Heater Frozen: Simple Solutions

Winter can bring its own set of challenges for homeowners, with the tankless water heater frozen being a particularly common issue. As temperatures plummet, the risk of your on-demand water heater succumbing to the cold intensifies.

To prevent potential damage and ensure continuous hot water flow, it’s essential to understand the steps you can take to protect your unit from freezing. The solutions range from simple maintenance tips to essential protective measures, all designed to keep the hot water running all winter long. Will your tankless water heater stand up to the winter chill?

Stay tuned for expert advice on safeguarding your appliance against freezing temperatures.

How to Fix Tankless Water Heater Frozen: Simple Solutions

Understanding Why Tankless Water Heater Frozen

Tankless water heaters work by heating water only when you need it. This means there is no storage tank to keep water warm at all times. During periods of very cold temperatures, the pipes carrying cold water to the heater can freeze. This is because tankless heaters do not generate as much heat when not in use compared to a storage water heater.

The most common areas for freezing to occur are:

  • Where the cold water supply line enters the unit
  • Inside the unit near the cold water inlet

Another reason is insufficient insulation around the pipes. The temperature sensor in some models can also freeze and prevent the unit from activating. Understanding why freezing occurs can help you address the root cause.

Identifying the Tankless Water Heater Frozen Problem

If your tankless water heater has frozen, the first sign will be the lack of any hot water. You may also hear unusual noises coming from the unit. To confirm freezing, feel around the cold water supply line and inlet area. If any section feels solid or icy cold, then freezing has likely occurred.

You can also check for error codes on the display panel. Common codes for freezing are Er 01, F9, or F11. The unit may shut off automatically as a safety measure when freezing is detected. Identifying the problem signs early helps solve it before lasting damage happens.

Warming Up Pipes and Unit Internally

Once you confirm freezing, start by warming the exterior pipes and unit using a towel soaked in warm water. Be very careful while doing this as you do not want anyone getting burned. Focus on the areas identified as prone to freezing.

You can also try using a hair dryer on its lowest heat setting to gently warm up frozen sections. Point the dryer vents directly at the frozen spots and move it around slowly. Keep monitoring for any improvement in flexibility.

As pipes and sections start to thaw, water may begin dripping out. This is normal as ice is melting. Continue warming efforts until all frozen areas feel soft and malleable again. Take utmost care while working near live electrical components inside the unit.

Insulating Exterior Piping

After internal warming, shift focus to insulating exterior piping better. Adding extra insulation wrapping externally helps prevent future freezing episodes. Make sure to add insulation over the entire length of the exposed cold water supply line right up to where it enters the unit.

You can use pre-split insulating sleeves available at home stores. Slip it over the pipe and seal the seams properly using insulating tape. For additional protection, you can wrap insulation with a self-sealing membrane or plastic sheeting securely using zip ties. Proper insulation is key to avoid freezing recurrence.

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Using Heat Sources Carefully

If internal and external warming is not working even after a long effort, as a last resort you can try using safe heat sources around the unit with an insulation barrier in between. Never operate heat guns or torches directly on plastic or metal parts as it can damage them.

Options like infrared heat lamps placed at a safe distance or even a hair dryer can potentially help in very stubborn cases. But be very cautious of fire risks and keep monitoring temperature levels closely. Disconnect power to the unit as added safety before using any direct heat methods.

Consulting a Professional

If none of the DIY solutions seem to work after giving sufficient time, it is best to call a licensed plumber or technician for inspection and repair. Frozen units may need additional disassembly and repair work that requires expertise. 

Professionals have the right tools and experience to properly diagnose problems. They can also advise on upgrades like electric heating cables if recurring freezing is an issue. This is how the professional will handle your tankless water heater frozen using the following steps:

  1. Inspection: The professional will begin with a thorough inspection of your unit, the cold water supply line, and other components to assess the extent of the freeze.
  2. Diagnosis: Next, they will diagnose the issue, determine the cause of the freeze, and evaluate the unit’s overall health to identify any potential long-term risks.
  3. Disassembly: In many cases, disassembly may be necessary to access frozen parts or address internal damage.
  4. Repair: The technician will carry out any repairs needed to fix damage caused by the freeze. This may include replacing parts, such as temperature sensors or valves.
  5. Reassembly: After repairs, the technician will reassemble your unit with care to ensure everything is back in proper working order.
  6. Testing: To confirm that the repairs are successful, the technician will conduct a series of tests. These may involve running the heater to check for correct operation and ensuring there are no leaks.
  7. Preventive Measures: They will recommend or install preventive measures like electric heating cables or advise on improved insulation to prevent future instances of freezing.

Prevention is Better Than Cure

The best solution is to prevent freezing from occurring in the first place rather than fixing it. Some precautions you can take are keeping the area around the water heater insulated and dry. Also, set your thermostat a few degrees higher during cold snaps.

Regularly inspecting for any signs of damage, especially aging insulation is important. Monitor for error codes and shut the unit off if you will be away from home for extended periods during winter. With proper maintenance and care taken, your tankless water heater should provide years of reliable hot water service. Don’t let the cold freeze your hot water – take preventative measures and stay warm all winter long.

Read More: Why is My Tankless Hot Water Heater Frozen?


The key to preventing your tankless water heater frozen lies in proactive maintenance and the implementation of protective measures. By insulating pipes, maintaining a warm ambient temperature, and considering recirculation systems or antifreeze, you can confidently safeguard your investment. Don’t let the cold weather leave you with the chill of unexpected repairs; a well-maintained heater means warm water, no matter the weather outside.

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