What is your water heater trying to tell you?
Tankless water heater error codes by brand and series
417 codes across 5 brands and 16 series. Find what the number on your display means on your exact unit — and whether the fix is a $30 descale, a replaceable part, or a call to a plumber.
Browse by brand
Jump straight to a code
These are the codes documented on more than one series, so each one opens a comparison rather than a guess. If yours is not here, it is on the full table.
Every code gets a verdict
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Descale it
Mineral scale causes a huge share of tankless faults. When that's your code, we show the safe DIY flush — usually about $30 in supplies.
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Replace a part
Some codes point to one specific component. We name the part and its typical price, so a repair quote can't surprise you.
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Call a pro
Gas, venting, and exhaust codes get one instruction only: stop and call a licensed professional. No exceptions.
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Just reset it
Some codes are a setting, a service reminder, or an interrupted cycle. When nothing is broken, we say so — and tell you the exact reset.
Start here
Why the series matters
The same code number can mean different things on different series of the same brand. Tankless Codes documents codes per series, transcribed from the manufacturer's own diagnostic manual, with the document and page cited on every page.
A concrete example, and you can see both halves of it on one page: Rinnai code 34 is the lime detecting thermistor on the hot water pipe of a SENSEI RX, and the combustion air temperature thermistor in the fan housing of an older non-SENSEI unit — a different part, in a different place, with a resistance range five times higher, and a different verdict on what it costs to fix. A brand-level answer gets that wrong half the time.