How to Protect an Exterior Tankless Water Heater from Freezing Temperatures

An exterior tankless water heater is an ideal solution for homes that require on-demand hot water without occupying indoor space. However, outdoor installation exposes the unit to weather conditions, especially freezing temperatures. Without proper precautions, cold weather can damage the unit, cause water lines to burst, and reduce the lifespan of your exterior tankless water heater.

In this article, we will provide a comprehensive guide on how to protect your exterior tankless water heater from freezing temperatures, ensuring safe and reliable operation during the winter months. This guide is tailored for homeowners, contractors, and anyone considering an outdoor hot water system.

Macro Outdoor Gas Water Heater S2

Understanding the Risks of Freezing for an Exterior Tankless Water Heater

An exterior tankless water heater operates by heating water instantly as it flows through the unit. In freezing conditions, the water inside the heater or its pipes can expand and freeze, leading to cracks in the heat exchanger or water lines. Common risks include:

• Burst water pipes connected to the unit

• Damaged internal components of the exterior tankless water heater

• Reduced performance or complete system failure

• Water leakage causing property damage

Because exterior tankless water heaters are fully exposed to ambient weather, protecting them from freezing is crucial for uninterrupted hot water supply and long-term durability.

Choose a Model with Built-In Freeze Protection

Many modern exterior tankless water heaters come with built-in freeze protection mechanisms. These features include:

• Automatic internal heating elements that activate when temperatures drop

• Insulated water passages to prevent freezing in cold weather

• Sensors that monitor water and ambient temperatures

When shopping for an exterior tankless water heater, prioritize models with built-in freeze protection. This reduces the risk of damage and eliminates the need for constant manual intervention during winter.

Install the Unit in a Sheltered Location

Proper placement is essential to protect your exterior tankless water heater from freezing. Consider the following installation tips:

• Mount the unit on a wall that is shielded from direct wind exposure

• Use overhangs or awnings to prevent snow, ice, and rain from directly contacting the heater

• Ensure the unit is not installed near areas prone to water accumulation or puddling, which may increase freeze risk

A well-chosen installation location enhances the effectiveness of built-in freeze protection and prolongs the life of your exterior tankless water heater.

Macro Outdoor Gas Water Heater S2

Insulate Pipes and Water Lines

Even with a freeze-protected exterior tankless water heater, the connected water pipes remain vulnerable. Proper insulation prevents freezing in exposed sections. Key steps include:

• Use foam pipe insulation sleeves or tape around all exposed hot and cold water lines

• Pay special attention to supply and return lines that run outside or through unheated spaces

• Insulate any pressure relief or drain pipes associated with the exterior tankless water heater

• Pipe insulation reduces heat loss and ensures the water reaches the unit at a safe temperature, minimizing the risk of freezing.

Install a Freeze Protection Kit

A freeze protection kit provides an extra layer of defense for exterior tankless water heaters. These kits may include:

• Heating cables or tape that wrap around water lines

• Temperature sensors that trigger automatic heating

• Drain valves that allow the system to empty water when temperatures drop

Using a freeze protection kit is especially important in regions where winter temperatures consistently fall below freezing for extended periods. This additional protection ensures your exterior tankless water heater remains operational even during extreme cold.

Drain the Unit During Extended Freezing Periods

If you anticipate prolonged periods of sub-zero temperatures and will not be using your exterior tankless water heater, draining the system is recommended:

• Turn off the water supply and electricity or gas to the unit

• Open all valves to allow water to completely drain from the unit and connected pipes

• Use a garden hose to remove residual water from low points

Draining the heater prevents ice from forming inside the heat exchanger, a common cause of damage in outdoor tankless units.

Use Recirculation or Continuous Flow in Cold Weather

For areas with intermittent freezing, running a small amount of water continuously through the exterior tankless water heater can prevent freezing:

• Even a slow drip maintains flow and prevents water from freezing

• Some systems have recirculation pumps designed for winter operation

• Ensure any recirculation setup is compatible with your exterior tankless water heater manufacturer guidelines

Continuous flow is an effective temporary solution when built-in freeze protection is limited.

Regular Winter Maintenance

Preventive maintenance is essential to safeguard your exterior tankless water heater during freezing months:

• Check for signs of frost or ice accumulation around the unit

• Inspect pipes for cracks or leaks before cold weather

• Ensure all insulation and heating cables are intact and functional

• Flush the system periodically to remove sediment that can freeze and block flow

A proactive maintenance routine reduces emergency repairs and ensures the unit operates efficiently.

Consider High-Quality Materials

Choosing an exterior tankless water heater made from high-quality, weather-resistant materials can improve freeze resistance:

• Stainless steel or corrosion-resistant heat exchangers

• UV-resistant housing to withstand sun and snow exposure

• Durable valves and fittings that tolerate cold contraction

Investing in a premium exterior tankless water heater minimizes the risk of freeze-related damage and extends the service life of the system.

Monitor Weather Conditions and Take Preventive Action

Homeowners should monitor local weather forecasts and respond proactively:

• Before an expected freeze, ensure insulation and heating systems are functioning

• Consider temporary coverings or enclosures for extreme cold events

• Know how to safely drain the unit in an emergency

• Active monitoring and quick action can prevent costly damage to your exterior tankless water heater.

Summary: Protecting Your Exterior Tankless Water Heater

Protecting an exterior tankless water heater from freezing requires a combination of planning, installation best practices, and preventive measures:

1. Choose a model with built-in freeze protection

2. Install in a sheltered, well-chosen location

3. Insulate all exposed pipes and water lines

4. Use a freeze protection kit with heating cables and sensors

5. Drain the unit during extended periods of freezing

6. Employ continuous flow or recirculation when necessary

7. Perform regular winter maintenance

8. Select durable, weather-resistant materials

9. Monitor weather conditions and act proactively

By following these steps, you can ensure your exterior tankless water heater remains safe, operational, and efficient throughout the cold season.

Protecting your exterior tankless water heater from freezing is critical for maintaining consistent hot water supply and extending the lifespan of your unit. With proper installation, insulation, and preventive measures, homeowners can enjoy reliable performance and peace of mind even in the harshest winter conditions.