Tankless water heater error codes
What is your water heater trying to tell you?
Look up the error code for your exact brand and series — what it means on your unit, and whether the fix is a $30 descale, a replaceable part, or a call to a plumber.
Browse by brand
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Rinnai
In progress
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Navien
In progress
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Rheem
In progress
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Noritz
In progress
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Takagi
In progress
The first code libraries are being verified against manufacturer manuals right now — Rinnai ships first, with Navien, Rheem, Noritz, and Takagi to follow.
Every code gets one of three verdicts
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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.
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 source and the date we verified it shown on every page.