Outdoor tankless water heaters provide an endless supply of hot water without taking up valuable indoor space. However, operating a tankless water heater outside in freezing temperatures comes with some unique challenges. If the proper precautions aren’t taken, critical components can freeze and rupture, causing extensive damage.
Fortunately, there are steps you can take to keep your outdoor tankless unit running smoothly through the winter. This comprehensive guide will provide you with everything you need to know to prevent freezing and ensure your outdoor tankless water heater lasts for years to come.
Why Tankless Water Heaters Freeze Outdoors
Before getting into winterization methods, it’s important to understand why outdoor tankless water heaters are susceptible to freezing in the first place.
There are a few key factors that put outdoor units at risk when temperatures drop:
- Exposure to cold air – Unlike indoor units that are protected from the elements, outdoor tankless heaters have no insulation or shelter from freezing ambient temperatures. Prolonged exposure can cause internal components to reach freezing conditions.
- Small amount of standing water – All tankless heaters contain some residual water in internal pipes, heat exchanger coils, and other components. If temperatures remain below freezing for extended periods, this standing water can freeze and expand, leading to cracked pipes and ruptured seals.
- Lack of use – Running water through the system provides warmth that prevents freezing. But outdoor units that aren’t used regularly can sit dormant for days or weeks, allowing ice crystals to gradually form inside.
By understanding these vulnerabilities, you can take the proper precautions to safeguard your outdoor heater during cold weather.
Preventing an Outdoor Tankless Water Heater from Freezing
There are several effective methods to keep your outdoor tankless unit running smoothly through sub-freezing conditions:
1. Insulate External Pipes and Fittings
One of the most important steps is insulating all external water connections leading to and from the heater. This includes:
- Inlet and outlet pipes
- Shutoff valves
- Flexible supply lines
- Pressure relief valve
Use heating cable or heat tape wrapped around pipes, then insulate with foam pipe insulation. The heating cables will maintain temperatures above freezing.
Be sure to use UL-approved products rated for outdoor use. Carefully follow all manufacturer instructions to avoid overheating or fire hazards.
2. Install a Freeze Protection System
Purpose-made freeze protection systems are available that circulate warm water through the heater whenever exterior temperatures drop below a set level, typically 38°F.
These systems include:
- Outdoor-rated mini-circulation pump
- Thermostat to activate the pump at low temps
- Bypass valve to circulate water internally
The pump circulatessupply water or glycol through the heat exchanger to prevent freezing. This provides freeze protection without actually activating the burner.
3. Use an Indoor Installation
The most foolproof option is to install the entire tankless water heater indoors and run only the intake and outlet pipes outside.
This allows the unit to be fully protected from freezing air. Only the pipes require insulation and heating.
Indoor mounting is ideal when:
- The heater is close to an exterior wall
- Non-combustible venting is available
- Unit weight can be supported
Just be sure to account for proper exhaust venting to the outdoors.
4. Add Glycol to the Water Supply
One way to protect both the heater and attached plumbing is adding RV antifreeze or glycol to the water supply.
Glycol acts as antifreeze to reduce the freezing point of the water. Most manufacturers recommend a 50/50 glycol/water mixture for temperatures below -30°F.
Just be aware that glycol can be corrosive to internal components over time. Annual flushing is required.
5. Install a Condensation Collector
Certain tankless heaters produce water vapor exhaust that can accumulate and freeze on exterior vent piping. Installing a condensation collector reduces this risk.
The collector captures moisture before it exits the vent and drains it away from the heater. This prevents frozen vent blockages.
6. Maintain Smart Home Automation
Using smart controls can help maintain safe temperatures automatically. Thermostats and sensors can activate heat tapes and circulation pumps once exterior temperatures drop below preset levels.
Just ensure the automation system has power backup in case of electrical outages. Relying solely on smart controls is risky.
7. Provide a Weatherproof Enclosure
For the highest level of protection, enclosing the entire heater in a weatherproof housing is effective. Look for enclosures designed specifically for tankless water heaters.
Properly sealed housings prevent exposure to freezing air and precipitation while still providing adequate ventilation.
Winterizing an Outdoor Tankless Unit
Along with preventative measures, proper winterization procedures are key to avoiding freeze damage. Here are the recommended steps when preparing your outdoor tankless water heater for winter:
Shut Down and Drain the System
Start by performing a complete system shutdown:
- Turn off the power and gas supply to the heater.
- Close the main water supply valve.
- Open all hot water taps to drain residual water from lines.
- Disconnect and drain inlet/outlet piping if possible.
Draining all water from the system prevents freeze expansion damage.
Clear Debris from Enclosures
Make sure the exterior of the heater is free of dirt, leaves, nests or other debris that can allow moisture inside.
Inspect all enclosures, vents and drain lines to ensure they are unobstructed. Clogged vents or drains can lead to freeze damage.
Disconnect All Hoses and Filters
Remove any exterior hoses or water filters connected to the heater. Move filtration systems indoors if possible.
Store hoses and cartridge filters to prevent cracking and warping from freezing.
Insulate Pipes and Fittings
Make sure all exposed pipes and fittings have adequate foam insulation and heating tape/cables installed. This includes:
- Water inlet and outlet piping
- Gas supply piping
- Condensation drain lines
- Pressure relief valve line
Refer to the section above on pipe insulation for details.
Add Antifreeze to Pipes
For additional protection, introduce RV antifreeze into pipes leading to the heater:
- Disconnect inlet and outlet water lines.
- Connect antifreeze-rated hoses to inlet and outlet ports.
- Open inlet valve and run antifreeze through system.
Repeat this process for any condensation drain lines as well.
Check Heat Tape and Heating Systems
Verify any electric heating tapes, heat trace cables and freeze protection circulation pumps are in good working order:
- Inspect for damage and replace if needed.
- Ensure power supply is active.
- Test operation and set thermostat if equipped.
Consider Removal as an Option
If you live in an area with extreme winters, completely removing the outdoor heater may be wise. This eliminates any risk of freezing.
Store the unit in a dry location until temperatures are reliably above freezing in spring.
Just be very careful when handling and transporting the heater to avoid damage.
Maintaining and Monitoring Through Winter
Freeze prevention for outdoor tankless water heaters doesn’t stop once winter arrives. Ongoing maintenance and monitoring is required to avoid issues:
Periodically Start Up the Heater
Run the heater at regular intervals throughout winter, at least monthly. This circulates warm water to prevent freezing.
Without use, standing water in pipes can gradually reach freezing temperatures.
Frequently Check Enclosures and Vents
Inspect the exterior of the heater often to make sure vents remain clear and enclosures intact.
Remove any accumulated snow, ice or debris blocking vents or drain lines.
Confirm Heating Systems Function Properly
Check that all heating tapes, heat trace systems and circulation pumps are activating as intended.
Repair or replace any failed components immediately to avoid pipe freezing.
Monitor Antifreeze and Glycol Levels
If using internal antifreeze, test levels periodically and top up as needed to maintain freeze protection.
Also check glycol/water mixtures in any supply pipes or headers.
Address any External Leaks Immediately
Leaks that develop in exterior pipes, valves or fittings should be addressed promptly. Escaping water that then freezes can lead to major rupture damage.
Safely Using the Heater in Winter
With the proper winterization and maintenance, you can safely use your outdoor tankless water heater even in freezing conditions:
Run a High Temperature Setpoint
Keeping the unit’s setpoint at 125°F or higher helps prevent freezing, even if some water remains in internal piping.
Just be aware of scalding risks at very high temperatures.
Insulate Exterior Piping
Any exposed inlet/outlet piping should be insulated while the heater runs in winter. This helps mitigate heat loss.
Shut off and drain pipes again after each use.
Allow a Warm-Up Period
Don’t draw water right away when first starting up a cold unit. Let it run 5+ minutes to warm up internal components and melt any ice.
Expect Lower Output Temps
The output water temperature may not reach its typical levels until all internal piping has warmed.
Monitor temps closely to ensure adequate hot water supply.
Only Use for Brief Periods
In extreme cold, only run the heater as long as necessary to conserve heat. Frequent and prolonged shutdown allows internal freezing.
Shut Down Properly After Use
Always shut down then drain the system after each use in freezing weather. Never shut off power to a full, wet system.
Following these usage guidelines will provide protection from freeze damage. But ongoing monitoring and maintenance is still critical.
Troubleshooting Frozen Tankless Water Heaters
Even with diligent maintenance, partial freezing can still occur in outdoor units. Here are some troubleshooting steps if you suspect your tankless heater has frozen components:
Confirm Power and Gas Supply
Loss of power or gas shutoff can allow residual water to freeze inside the dormant heater.
Restore both supplies if interrupted.
Inspect for Ice Blockages
Check for visible ice accumulations blocking exterior vents, drain lines, or sections of piping. Carefully melt any blockages using a hair dryer if possible.
Never attempt to thaw the heater’s internal heat exchanger yourself.
Check for Leaks
Partial freezing can fracture pipe fittings, valves and seals. Inspect closely for leaks with the heater off and drained.
Repair any leaks before resuming operation.
Test Heater Activation
Attempt to activate the heater. Failure to ignite or power on could indicate an electrical component or gas valve frozen.
Carefully thaw the component if possible and test again.
Call a Professional if Needed
If you suspect internal freezing but cannot pinpoint or resolve the issue, call a professional for assistance. Internal repairs should only be done by qualified technicians.
Completely resolving all freezing issues is critical before putting the heater back into service.
Preventing Future Freezing Problems
If your outdoor tankless unit did suffer freeze damage, make sure to implement preventative measures moving forward:
Insulate All Components and Pipes
Any parts or plumbing that froze previously should now be better protected with insulation and heat trace systems. Prevent recurrences.
Install a Freeze Protection System
Consider adding an automatic circulation pump system for the most comprehensive freeze protection.
Mount the Heater Indoors
If outdoor freezing remains an issue, the best solution can be bringing the entire heater inside. No more worries about exterior temperatures.
Use a Higher Glycol Concentration
If using glycol antifreeze, increase the concentration to provide protection at lower temperatures.
Enclose in a Weatherproof Housing
Install a sealed weatherproof enclosure rated for tankless heaters to surround the entire unit.
With the proper combination of insulation, heating, enclosures and glycol, outdoor tankless water heaters can be protected against even extreme freezing conditions. Don’t wait for damage to occur before taking action.
Frequently Asked Questions About Freezing Tankless Water Heaters
To summarize key information on protecting outdoor tankless water heaters from freezing temperatures, here are answers to some frequently asked questions:
Why are outdoor tankless water heaters prone to freezing?
Exposure to freezing air, lack of use allowing water to stagnate inside, and small amounts of standing water make outdoor tankless units vulnerable to freezing damage.
What temperatures will cause freezing problems?
Freezing issues can occur once exterior temperatures drop below 32°F for extended periods. Problems intensify below 10°F.
How can I prevent freezing in my outdoor tankless heater?
Insulating pipes, installing freeze protection systems, maintaining smart home automation, adding glycol, and weatherproof enclosures can all help prevent freezing.
What’s the best way to winterize my outdoor heater?
Shutting down, draining the system, adding antifreeze, insulating pipes, and checking heating systems helps properly winterize outdoor units.
What should I do if my heater does freeze up?
Troubleshoot potential causes like loss of power/gas, vent blockages, leaks, or component freezing. Seek professional help with internal freezing issues.
How can I stop freezing problems from recurring?
Better insulation, freeze protection systems, indoor mounting, higher glycol concentrations, and weatherproof enclosures can help prevent future freezing.
Key Takeaways on Preventing Outdoor Tankless Water Heaters From Freezing
Protecting outdoor tankless water heaters from catastrophic freezing is critical for trouble-free operation through frigid winters. Keep these key points in mind:
- Exposure to freezing air, stagnant water, and small water volumes put outdoor heaters at high risk of freezing damage.
- Insulate all external pipes and fittings to maintain above-freezing temperatures.
- Install purpose-made freeze protection systems to automatically circulate warm supply water when needed.
- Fully drain and winterize units properly before winter hits.
- Provide weatherproof enclosures for the safest protection from the elements.
- Monitor and maintain freeze prevention systems all winter long.
- Address any freezing issues quickly to avoid severe rupture damage.
Following a diligent winterization and maintenance regimen will keep your outdoor tankless water heater running smoothly even in the coldest conditions. Don’t cut corners that could lead to an expensive frozen and cracked heat exchanger. With proper care, your outdoor heater can supply endless hot water for many years to come.