Rinnai · Water heater
Code 63 Low flow in recirculation loop
What this code means
Specific to models with a built-in recirculation pump (like the RUR series) — flow in the recirc loop has dropped below the pump's minimum.
Most likely causes
- Clogged recirculation line
- Failing recirculation pump
- Closed isolation valve on the loop
What to try first
Check that any valves on the recirculation loop are fully open.
Good news: this one is often fixable without a service call. If it persists after the steps above, have it looked at.
FAQ
What does Rinnai error code Code 63 mean?
Low flow in recirculation loop. Specific to models with a built-in recirculation pump (like the RUR series) — flow in the recirc loop has dropped below the pump's minimum.
Can I fix Rinnai code Code 63 myself?
Often, yes. Check that any valves on the recirculation loop are fully open.
What causes Rinnai code Code 63?
The most common causes are: clogged recirculation line; failing recirculation pump; closed isolation valve on the loop.
Other Rinnai water heater codes
All Rinnai water heater error codes →
Other water heater brands: Rheem · Ruud · Navien · Noritz · Takagi · A.O. Smith · Bradford White · State / American · Generic electric · Generic tankless
This information may contain errors or not apply to your exact model — always double-check it against your appliance's own manual before acting. If there's any chance of a gas, fire, electrical, carbon monoxide, or other safety hazard, stop and call a licensed professional or the appropriate agency (e.g. your gas utility) instead of relying on this page alone.