Water heater error code lookup

Pick a brand, then type the code — a two-digit tankless code, a flash count, or a display code like E110 — to get the meaning, with a link to the full page for that code.

Brand

Code or flash count

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This lookup needs JavaScript. Without it, browse by brand instead: Rinnai, Navien, Rheem, AO Smith.

Before you trust the count

Water heater codes are model-specific — a code that means one thing on a Rinnai tankless unit can mean something else entirely on a Navien or an AO Smith tank model, so confirm the brand (and check the "applies to" line on the result page) before assuming a fix.

Safety. A code lookup tells you what the control board detected, not that a fix is safe to do yourself. Anything involving the gas valve, burner, heat exchanger, or venting is work for a licensed technician, and a safety device that trips more than once is a reason to stop resetting it and call someone.

How this works

The lookup runs entirely in your browser from a small JSON file — nothing you type is sent anywhere. It searches every code page on this site, each of which cites the source it was written from. The one-line meanings here are summaries; the linked page has the full entry — causes, what's safe to check, and when to call a professional.

This site is an independent reference, not a substitute for a licensed plumber or electrician. Pages are written with AI assistance from the sources listed on each page and checked against them before publishing.