About Tankless Codes
Tankless Codes is a reference site with one job: when your tankless water heater shows an error code, tell you what that code means on your exact brand and series — and whether the fix is a DIY descale, a replaceable part, or a call to a licensed plumber.
Why "series" is the whole point
Most pages about error codes answer for a brand in general. But manufacturers renumber and redefine codes between product generations: the same two digits can mean a scale warning on one series and an ignition fault on another. Answering at the brand level is how people end up replacing the wrong part. Every code page on this site is written for one specific series.
How pages are researched
- Every code meaning is transcribed, in our own words, from the manufacturer's own diagnostic documentation for that exact series.
- Every code page cites its source document, with a link and the date we last verified it. If we haven't verified a fact against a manual, it doesn't get published.
- Cost ranges are typical US figures for parts and labor, provided to help you sanity-check a repair quote — actual prices vary by region and installer.
What this site will never tell you to do
Gas appliances can hurt people. This site never publishes instructions for working on gas lines, venting or exhaust, or for bypassing a unit's safety lockouts. Codes involving gas, ignition, or exhaust always carry the same instruction: stop and call a licensed professional. And the standing rule on every relevant page: if you smell gas, leave the area and call your gas utility from outside — do not restart the unit.
Independence
Tankless Codes is independently researched and maintained. It is not affiliated with, sponsored by, or endorsed by Rinnai, Navien, Rheem, Noritz, Takagi, or any other manufacturer. All trademarks belong to their respective owners.
Spotted an error?
Accuracy is the entire value of this site. If a code meaning looks wrong for your unit, please tell us — corrections are verified against the manual and fixed fast.