Water Heater Error Codes by Brand
What your water heater's error code, flash pattern, or fault display actually means — sourced from manufacturer documentation, not guesswork.
Tank and tankless water heaters report problems in whatever language their control board speaks: a two-digit code on a tankless display, a blink count on a tank's status light, or a letter-and-number combination like E110. That code is genuinely useful information — it tells you what the unit detected — but it's usually buried in a PDF manual nobody keeps around. This site collects those codes by brand, explains what each one means in plain language, lists what causes it, what's safe to check yourself, and where the line is between a homeowner fix and a licensed technician's job.
Start with your brand
Know the code already?
Skip straight to it: the code lookup searches every code on this site by brand and by the code or flash count itself.
No code showing — just a symptom?
Sometimes the unit doesn't display anything useful, or you haven't found the display yet. Start from what's actually happening:
- No hot water from a tank water heater
- No hot water from a tankless water heater
- Pilot light won't light or won't stay lit
- Cold water sandwich effect on a tankless unit
- Error code flashing or blinking
- Leaking from the base or bottom
- Ignition failure
- Water not hot enough, or runs lukewarm
What repairs cost
Decoded the fault — now what does fixing it actually run? Honest cost ranges for the most common water heater repairs, sourced from published contractor rate guides, not a lead-generation quote form.
Independent, not affiliated
This site is not affiliated with, endorsed by, or sponsored by Rinnai, Navien, Rheem, AO Smith, or any other manufacturer named on it. Brand names are used only to identify which products a code belongs to. Read the full methodology.