Water Heater Error Codes: What the Blinking Lights Mean and How to Read Them
Modern water heaters (especially tankless and smart models) display error codes via LED lights or digital screens. These codes pinpoint the exact problem, whether it’s a sensor failure, a gas ignition issue, or a temperature error. Learning to read error codes saves you money by helping you explain the issue to a plumber and avoiding unnecessary diagnostics.
How to Read Error Codes
LED blinking patterns:
Most units use rapid or slow blinks in sequences. For example:
- 2 fast blinks, pause, 1 slow blink = code “2-1” or “21”
Digital displays:
- Show the code directly (e.g., “Error 12” or “F02”)
Color-coded lights:
- Red (error)
- Yellow (warning)
- Green (normal)
Check your manual. Every brand/model has a different code system.
Common Error Codes by Brand
Rinnai (Most Common)
| Code | Meaning | Action |
|---|---|---|
| 11 | Flame failure | Check gas supply, igniter |
| 12 | High temp limit | Lower thermostat, check relief valve |
| 14 | Gas valve error | Gas supply/pressure issue; call plumber |
| 16 | Water flow sensor error | Low water pressure or sensor failure |
| 20 | Ignition failure | No spark; check electrical connection |
Navien
| Code | Meaning | Action |
|---|---|---|
| E001 | Ignition failure | Check gas and igniter |
| E002 | Overheat | Lower temperature setting |
| E003 | Thermal fuse | Heat exchanger issue; call pro |
| E004 | Water flow error | Check for blockage |
Rheem
| Code | Meaning | Action |
|---|---|---|
| 01 | Ignition failure | Gas/igniter issue |
| 02 | High limit | Temperature too high |
| 03 | Flame sensor | Sensor misalignment/failure |
| 04 | Gas valve | Gas supply failure |
General Categories
Ignition codes (1X, 20):
Burner won’t light. Check gas is on, igniter has spark.
Temperature codes (12, 02):
Overheating. Lower thermostat setting, verify relief valve works.
Water flow codes (16, 04):
Insufficient water pressure. Check the inlet filter, descale if needed.
Sensor codes (flame sensor, temp sensor):
Component failure. Usually requires professional replacement.
DIY Troubleshooting Steps
Before calling a plumber:
- Check the manual for your model’s code meanings
- Verify gas is on (if gas unit)
- Check water supply is on and pressure adequate
- Restart the unit (turn off 30 seconds, turn back on)
If error persists, note the code and call a plumber.
When DIY Won’t Help
Call a plumber immediately if:
- Ignition codes persist after a restart
- Flame sensor codes (requires sensor replacement)
- Overheat/high-limit codes with an unresponsive thermostat
- Any gas smell
Prevention
Keep error codes rare by:
- Annual maintenance/descaling (prevents flow/temp codes)
- Maintaining water pressure (prevents sensor errors)
- Checking the gas supply regularly
Find Local Help
If you’re getting error codes and basic troubleshooting doesn’t help, a plumber can read the code and diagnose quickly.
- Salt Lake City: Water Heater Repair in Salt Lake City
- Browse all locations: Find Water Heater Services Near You
FAQ
Can I ignore an error code if the heater still produces hot water?
No. Codes indicate problems that will worsen. Address them within days.
Does restarting always clear error codes?
Sometimes. If the error returns, it’s a real problem, not a glitch.
Where do I find the manual for my heater?
Manufacturer websites have PDFs. Search “[Brand] [Model] manual.”
Sources and Update Policy
This article reflects error codes for 2026 water heater models and common troubleshooting practices.