Rheem Tankless Gas error codes
Rheem's own service pocket manual (SVC820) covers its gas tankless range as a single code table, marking which codes apply only to high-efficiency (condensing) units and which only to indoor installations. It does not enumerate model numbers, so neither do we — what matters for reading these codes is whether your unit is condensing (it has a condensate drain line and an acid neutralizer) and whether it is installed indoors. Codes 29A, 92 and 93 are condensing-only; codes 05 and 13 are indoor-only.
Not your models? Check the model-number decoder before you read the table below — the code numbers repeat across series and the meanings do not.
| Code | Error | Verdict |
|---|---|---|
| 1L | Lime build-up in the heat exchanger | DIY fix |
| 03 | Communication failure between units or controls | Call a pro |
| 05 | Improper burner combustion (indoor units) | Call a pro |
| 10 | Vent blockage or insufficient ventilation | Call a pro |
| 11 | No flame detected | Call a pro |
| 12 | Flame lost after ignition | Call a pro |
| 13 | Poor combustion detected (indoor units) | Call a pro |
| 14 | Overheat limiter tripped | Call a pro |
| 15 | Water temperature reached 207°F | Call a pro |
| 16 | Outlet water above the set point | Call a pro |
| 24 | Remote control buttons held down | DIY fix |
| 29 | Condensate not draining, or heat exchanger too cold | Call a pro |
| 31 | Inlet thermistor malfunction | Part replacement |
| 32 | Heat exchanger thermistor malfunction | Part replacement |
| 33 | Outlet thermistor malfunction | Part replacement |
| 34 | Ambient thermistor malfunction | Part replacement |
| 35 | Thermistor connected incorrectly | Call a pro |
| 51 | Gas control valve: flame present after shutdown | Call a pro |
| 52 | PGFR (modulating gas valve) malfunction | Call a pro |
| 61 | Blower motor speed fault | Call a pro |
| 65 | Water volume control valve malfunction | Part replacement |
| 66 | Water by-pass valve malfunction | Part replacement |
| 71 | Gas control valve: inlet solenoid malfunction | Call a pro |
| 72 | Flame detected before ignition | Call a pro |
| 76 | Remote control communication fault | Part replacement |
| 79 | Blower motor current fault | Call a pro |
| 80 | Gas control valve: flame detected after shutdown | Call a pro |
| 82 | Control board program chip malfunction | Call a pro |
| 90 | Vent blockage detected before ignition | Call a pro |
| 92 | Neutralizer needs replacing (warning) | Part replacement |
| 93 | Neutralizer must be replaced (lockout) | Part replacement |
| 99 | Vent blockage detected after shutdown | Call a pro |
| P1 | No hot water delivered | DIY fix |
Every entry above is transcribed from the manufacturer's diagnostic documentation for this exact series, with the source cited on each code page.