Error codes on tankless water heaters are the system's way of communicating a specific problem. These codes vary by brand, but most point to a handful of common issues. For homeowners and business owners with tankless water heaters in Charlotte, NC, understanding these signals is the first step toward getting the right repair done without the back-and-forth.
The Most Common Error Codes and What They're Telling You
Error codes vary by brand, model, and production year; always verify meanings in the manufacturer’s manual and contact a trained technician for safety-critical issues.
Here is what you will typically see:
Ignition Failure
Codes like Rinnai 11, Noritz 11, and Navien E003 mean the burner failed to light. Possible causes: interrupted gas supply, closed gas valve, weak/failed igniter, bad ignition transformer or control board, tripped external safety switches, or blocked venting that affects combustion air.
Flame Failure
Rinnai codes 12 and 14 fall here. The burner lit but could not hold a flame. Possible causes: low gas pressure, incorrect air/gas mixture, dirty or misaligned flame sensor/rod, restricted gas line, or weak gas regulator
Overheating and Temperature
Rinnai 61, Navien E012, and Noritz 90 indicate the unit exceeded its safe operating temperature. Common causes: scale/limestone buildup in the heat exchanger, restricted water flow, failed flow sensor, or blocked heat-exchanger passages. Preventive fix: descale per manufacturer schedule, install a water-softening or scale inhibitor system if local water hardness is high.
Water Flow and Pressure
Rinnai 16, Navien E110, and Noritz 16 signal that water flow is too low to activate the burner. Check: clogged inlet filter, partially closed isolation valve, minimum activation flow rate for that model (commonly 0.4–0.8 GPM), closed recirculation bypass, or failing flow sensor. Fixes: clean inlet filter, verify valves fully open, check/replace flow sensor, or adjust plumbing/recirculation setup to meet min flow.
Venting and Exhaust
Rinnai 52, Noritz 70, and similar codes point to restricted intake or exhaust. Urgent: blocked venting may cause carbon-monoxide backdraft. Immediate actions: turn unit off, ventilate area, test with a CO alarm, and call a licensed technician. Fixes: clear obstructions, confirm venting pipe routing and termination meet code, repair damaged vent components.
Gas Supply
Rinnai code 10 and similar pressure-related codes across brands indicate the unit is not receiving adequate gas. Check: closed service valves, gas meter issues, regulator failure, or undersized gas piping. Fixes: verify valves and meter, contact the gas utility for supply/regulator problems, and hire a licensed plumber to size or repair gas lines. Do not attempt to adjust gas pressure yourself.
Safety note: blocked venting or gas faults can produce carbon monoxide. Ensure a working CO alarm on each level and call a pro immediately for venting or gas codes
Sensor Failure
Thermistor codes like Rinnai 65 and 66 mean a temperature sensor is reading incorrectly or has failed. The unit cannot regulate heat without accurate sensor input, so it shuts down as a precaution.
Control Board and System Errors
Navien E407 and E516 fall into this category. Troubleshoot steps: record exact codes, attempt a controlled reset per manual, inspect harnesses and connectors, check for firmware updates. If persistent, board-level diagnosis or replacement by a trained technician is required.
When a Reset Is Not Enough
Some codes can be cleared with a simple power cycle. Others come back within minutes. If an error code returns after resetting, it’s likely that the root cause has not been addressed. Ignoring repeat codes can lead to full unit shutdowns and, in some cases, voided warranties. This is where professional tankless water heater repair becomes necessary rather than optional.
Frequently Asked Questions About Error Codes
What does it mean if my unit shows different codes each time?
Multiple rotating codes usually point to a bigger underlying issue, such as a failing control board or persistent water quality problems. Get it inspected before it compounds.
Can I look up error codes myself?
Yes. Your owner's manual is the most reliable source, as code meanings differ by brand and model.
Does tankless water heater installation affect how often I see error codes?
It can. Improper sizing, incorrect gas line connections, or poor venting during installation are common reasons units throw codes frequently from the start.
Know the Code. Call the Right Plumber.
E.R. Plumbing Services has served the Charlotte area since 1997. Our highly trained technicians are available for 24/7 emergency plumbing services and log exact error codes, share diagnostic reports, and follow manufacturer procedures.
Call us for a diagnostic visit.
