A blinking red light on a tankless water heater typically indicates a malfunction or error; check the manual for specific error codes and troubleshooting steps.
A blinking red light on your tankless water heater signals trouble. Don’t panic – this guide explains what causes it and how to fix common issues yourself before calling a pro.
What Does a Blinking Red Light Mean?
The flashing red light is your heater’s way of showing an error. Different brands use different codes, but common causes include:
- Overheating from mineral buildup
- Low water flow
- Ignition failure
- Gas supply issues
- Electrical problems
Takagi T-K2 Specific Codes
For Takagi models like the T-K2 mentioned in our sources:
| Light Pattern | Likely Issue |
|---|---|
| Flashing red, green off | Ignition or flame detection problem |
| Solid red | System shutdown (serious fault) |
Step-by-Step Troubleshooting
1. Check for Simple Fixes First
Before diving deep:
- Power cycle the unit (unplug for 30 seconds)
- Verify water flow exceeds 1 GPM (gallons per minute)
- Check for tripped circuit breakers
- Ensure gas supply valve is open
2. Clean the Flame Sensor
As our source mentioned, a dirty flame sensor causes many issues:
- Turn off power and gas supply
- Locate the sensor (consult manual)
- Gently clean with Scotch-Brite pad
- Reassemble and test
This simple fix worked for the Takagi owner in our source material after 9 years of use.
3. Descale the Heat Exchanger
Mineral buildup reduces efficiency and causes overheating. Follow these steps:
- Purchase a tankless descaling solution
- Connect a circulation pump (or use the unit’s service valves)
- Flush according to manufacturer instructions
- Rinse thoroughly with clean water
When to Call a Professional
Some issues require expert help:
- Gas leaks (smell gas? evacuate and call 911)
- Electrical faults
- Persistent error codes after troubleshooting
- Carbon monoxide concerns (install detectors!)
Advanced Component Checks
For persistent issues, these components may need testing:
| Component | Test Method |
|---|---|
| Flow sensor | Measure resistance values |
| Gas valve | Check voltage and operation |
| Control board | Inspect for burnt components |
Preventative Maintenance Tips
Keep your tankless heater running smoothly:
- Annual descaling (more in hard water areas)
- Clean inlet filter quarterly
- Inspect venting annually
- Consider a water softener if you have hard water
Signs You Need Replacement
If your unit is over 10 years old and showing multiple issues, consider upgrading to a newer model with better efficiency and reliability.
For more on home temperature solutions, see our guide to home temperature regulation devices.
