Introduction
Navien tankless water heaters are known for their energy efficiency, compact design, and reliable performance. But like any appliance, they can occasionally run into problems. If you’re dealing with hot water issues, error codes, or other performance problems, this guide will walk you through Navien tankless water heater troubleshooting step by step.
Whether you own a Navien NPE-240A, NPE-180S, or another model, this article covers the most common Navien water heater issues, their causes, and easy DIY fixes (plus when to call a professional).
Common Navien Tankless Water Heater Problems
1. No Hot Water
Possible Causes:
- No gas or water supply
- Flow sensor malfunction
- Clogged filter or heat exchanger
- Incorrect temperature setting
Troubleshooting Tips:
- Make sure the gas valve and water supply are fully open.
- Check if the unit is plugged in and the power switch is ON.
- Clean the inlet water filter.
- Confirm that the minimum flow rate is met — usually around 0.5 GPM.
2. Navien Error Codes
Your Navien unit will display a specific error code on its screen. Here are some of the most common:
| Error Code | Meaning | Solution |
|---|---|---|
| 003 | Ignition failure | Check gas supply, clean igniter |
| 012 | Flame loss | Inspect flame rod and gas pressure |
| 016 | Overheating | Flush heat exchanger, clean filters |
| 027 | Air pressure abnormal | Ensure proper venting and clear air intake |
| 038 | Condensate backup | Clear drain line, inspect trap |
| E110 | Exhaust overheating | Check for vent blockages |
For a full list, refer to your Navien user manual or the official Navien error code guide.
3. Water Too Hot or Not Hot Enough
Possible Causes:
- Thermostat setting too high or low
- Scale buildup in heat exchanger
- Inconsistent water flow
Fixes:
- Adjust the temperature setting to your desired range (typically 120°F–125°F).
- Flush the system with a descaling solution to remove mineral buildup.
- Make sure faucets and fixtures are not restricting water flow.
4. Unit Making Noise (Banging or Humming)
Likely Causes:
- Mineral buildup
- Loose components
- Air in the line
Solutions:
- Descale your heater using a vinegar or CLR flush.
- Check mounting brackets and internal components.
- Bleed the air out of the water line.
5. Navien Won’t Turn On
What to Check:
- Power cord is securely plugged in
- Breaker hasn’t tripped
- Unit is not in “Vacation” mode
If the unit still won’t power on, call Navien technical support at 1-800-519-8794.
Preventative Maintenance Tips
Keeping your Navien water heater in great shape prevents many of the issues above. Follow these tips:
- Flush the system every 6–12 months to prevent scale buildup
- Clean inlet water filters monthly
- Inspect and clear air intake/exhaust vents regularly
- Test for error codes every few weeks
- Schedule annual professional servicing
Tools You May Need for DIY Maintenance
- Phillips screwdriver
- Bucket
- White vinegar or descaling solution
- Submersible pump (for flushing)
- Garden hose
- Clean rags
When to Call a Professional
If you’ve tried all basic troubleshooting steps and your Navien heater still isn’t working properly, it’s time to call a certified HVAC or plumbing technician. You should also get professional help if:
- You smell gas
- The error code repeats after a reset
- There’s water leakage inside the unit
- You’re unfamiliar with working on gas appliances
Final Thoughts
Navien tankless water heaters are built to last, but even the best systems require occasional care. By following these troubleshooting steps, you can save time, avoid costly repairs, and ensure your home always has reliable, on-demand hot water.
For persistent issues, don’t hesitate to reach out to Navien customer service or a licensed professional.
