Gas water heaters: E10 error code by brand
Tankless (continuous-flow) gas water heaters show "10" for combustion or air/exhaust problems. Treat it as a gas-safety warning.
| Brand | Code | Meaning (from the maker) | Region |
|---|---|---|---|
| Rinnai | 10 | Air supply or exhaust blockage: the heater cannot breathe in or vent out properly. | USA, Australia & worldwide |
| Noritz | 10 | Combustion abnormality: an early warning before the more serious code 90. | USA & Canada |
| Rheem | 10 | Abnormal low-rate combustion: call Rheem Service. | Australia |
Safety. If you smell gas, do not touch switches: leave, then call your gas emergency number from outside. Only a licensed gas fitter/plumber may open the unit, change venting or adjust gas pressure. Owners may check that outside vents are clear and reset the unit.
Why the same code means different things
Error codes are not standardised. Each manufacturer writes its own list, and even one brand can change it between model generations. That is why every page here names the brand, links the maker's own support page and shows the date we checked it. If your brand is missing, we have not yet found an official meaning: check the manual (often in a pocket on the back or inside the door, or on the maker's website by model number).