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Water flow control fault: tankless water heater / continuous flow hot water system codes by brand
A motorised water flow or bypass control valve is not moving or reporting correctly.
| Brand | Code | Meaning | What you can do |
|---|---|---|---|
| Rinnai | 05 | Bypass flow control failure | Safe checks first, then a pro |
| Rinnai | 65 | Water flow control failure | Safe checks first, then a pro |
| Rinnai | 66 | Bypass flow control fault | Call a pro |
| Navien | E434 | Water adjustment valve fault | Call a pro |
| Navien | E445 | Bypass mixing valve fault | Call a pro |