Rheem tankless water heater error codes
Rheem's gas tankless range splits into mid-efficiency and high-efficiency (condensing) units, and its service documentation treats them as one code table with the differences marked. Several codes exist only on the condensing units — the ones about condensate drainage and the acid neutralizer — and two more apply only to indoor installations. Rheem also separates warnings from errors: some codes let the unit keep running while it tells you something is wrong.
Pick your series below — Rheem code meanings are documented per series, because the same number can point to a different fault on a different generation.
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Tankless Gas
33 documented codes
Not sure which series you own? The model-number decoder matches the number on your rating label to the right table.
All Rheem codes in one table
| Code | Series | Error | Verdict |
|---|---|---|---|
| 1L | Tankless Gas | Lime build-up in the heat exchanger | DIY fix |
| 03 | Tankless Gas | Communication failure between units or controls | Call a pro |
| 05 | Tankless Gas | Improper burner combustion (indoor units) | Call a pro |
| 10 | Tankless Gas | Vent blockage or insufficient ventilation | Call a pro |
| 11 | Tankless Gas | No flame detected | Call a pro |
| 12 | Tankless Gas | Flame lost after ignition | Call a pro |
| 13 | Tankless Gas | Poor combustion detected (indoor units) | Call a pro |
| 14 | Tankless Gas | Overheat limiter tripped | Call a pro |
| 15 | Tankless Gas | Water temperature reached 207°F | Call a pro |
| 16 | Tankless Gas | Outlet water above the set point | Call a pro |
| 24 | Tankless Gas | Remote control buttons held down | DIY fix |
| 29 | Tankless Gas | Condensate not draining, or heat exchanger too cold | Call a pro |
| 31 | Tankless Gas | Inlet thermistor malfunction | Part replacement |
| 32 | Tankless Gas | Heat exchanger thermistor malfunction | Part replacement |
| 33 | Tankless Gas | Outlet thermistor malfunction | Part replacement |
| 34 | Tankless Gas | Ambient thermistor malfunction | Part replacement |
| 35 | Tankless Gas | Thermistor connected incorrectly | Call a pro |
| 51 | Tankless Gas | Gas control valve: flame present after shutdown | Call a pro |
| 52 | Tankless Gas | PGFR (modulating gas valve) malfunction | Call a pro |
| 61 | Tankless Gas | Blower motor speed fault | Call a pro |
| 65 | Tankless Gas | Water volume control valve malfunction | Part replacement |
| 66 | Tankless Gas | Water by-pass valve malfunction | Part replacement |
| 71 | Tankless Gas | Gas control valve: inlet solenoid malfunction | Call a pro |
| 72 | Tankless Gas | Flame detected before ignition | Call a pro |
| 76 | Tankless Gas | Remote control communication fault | Part replacement |
| 79 | Tankless Gas | Blower motor current fault | Call a pro |
| 80 | Tankless Gas | Gas control valve: flame detected after shutdown | Call a pro |
| 82 | Tankless Gas | Control board program chip malfunction | Call a pro |
| 90 | Tankless Gas | Vent blockage detected before ignition | Call a pro |
| 92 | Tankless Gas | Neutralizer needs replacing (warning) | Part replacement |
| 93 | Tankless Gas | Neutralizer must be replaced (lockout) | Part replacement |
| 99 | Tankless Gas | Vent blockage detected after shutdown | Call a pro |
| P1 | Tankless Gas | No hot water delivered | DIY fix |
Each code links to a full page: what the manual says for that exact series, the likely fix, and what it should cost.