To prevent an outdoor water heater from freezing, insulate the unit, use heat tape, and maintain a consistent power supply to keep water circulating.
Outdoor water heaters are vulnerable to freezing temperatures, which can cause costly damage. Unlike indoor units, they lack natural insulation from your home’s warmth. This guide covers proven methods to protect your investment and ensure hot water all winter.
Why Outdoor Water Heaters Freeze
Outdoor units face three main freezing risks:
- Exposed piping: Water lines lose heat faster when exposed to wind
- No ambient warmth: Lacks household heat that protects indoor units
- Power dependence: Freeze protection systems fail during outages
Critical Components at Risk
| Component | Freeze Damage Risk |
|---|---|
| Heat exchanger | High – Cracks when water expands |
| Water valves | Medium – Seals can fail |
| Condensate drain | High – Ice blocks drainage |
5 Essential Freeze Protection Methods
1. Insulate All Exposed Pipes
Use foam pipe insulation (minimum R-3 rating) on all water lines. For extreme climates, combine with heat tape that automatically activates below 40°F.
Pro Tip:
Wrap valves and elbows with extra insulation – these areas freeze first.
2. Maintain Power Supply
Most units need electricity for freeze protection. Consider:
- Battery backup (minimum 8-hour runtime)
- Portable generator with automatic transfer switch
- For gas models, keep pilot light on for residual heat
3. Create a Wind Barrier
Build a simple enclosure using:
- Pressure-treated wood frame
- Insulated panels (leave 12″ clearance around unit)
- Vented door for airflow
4. Install Recirculation System
A recirculation pump keeps water moving through pipes. Options include:
- Dedicated return line (most effective)
- Thermostatic valve system
- Timer-controlled operation
5. Drain for Long Absences
If leaving for 48+ hours in freezing weather:
- Turn off water supply
- Disconnect power/gas
- Open all drain valves
- Use air compressor to blow out remaining water
Emergency Thawing Procedures
If your unit freezes:
- Turn off power immediately
- Open nearest hot water faucet
- Apply heat with hair dryer (never open flame)
- Check for leaks once thawed
- Contact professional if damage suspected
When to Call a Professional
Seek help if you notice:
- Water leakage
- Error codes on display
- Unusual noises during operation
- No hot water after thawing
Climate-Specific Recommendations
Mild Winters (Rarely below 20°F)
Basic insulation plus pipe heating cables should suffice. The U.S. Department of Energy recommends maintaining at least 1/2″ foam insulation on all pipes.
Severe Winters (Below 0°F common)
Consider these advanced measures:
- Insulated enclosure with thermostatically controlled heater
- Underground pipe routing below frost line
- Whole-house generator backup
For extreme cold, indoor propane heaters can provide supplemental warmth to utility areas.
Manufacturer-Specific Tips
Navien Units
Enable recirculation mode in settings. Keep power connected at all times – the freeze protection works even when unit appears off.
Rinnai Models
Use the proprietary frost protection kit. Never block air intake vents, as this reduces freeze protection effectiveness.
EcoSmart Electric
These require 240V power for freeze protection. Consider a UPS battery backup sized for your model’s wattage.
