Recirculation low flow
Displayed as: 63
Rinnai's RU series installation and operation manual lists diagnostic code 63 as "Recirculation Low Flow". The manual's checks are: ensure the bypass plug is removed and the bypass filter is installed (in crossover-valve recirculation mode); ensure both the inlet water filter and the bypass filter are clean and free of debris; ensure the parameter settings are correctly set for recirculation mode; ensure the pump supply voltage is present; and ensure air is removed from the recirculation line.
Applies to
This code and wording come from manual 100000467 for the RU series and applies to installations using Rinnai's recirculation features, including crossover-valve mode. The cross-series document 100000652 applies the code across the generations it covers.
- Rinnai SENSEI RU (Super High Efficiency Plus condensing)
- Rinnai RU130iN
- Rinnai RU160iN
- Rinnai RU180iN
- Rinnai RU199iN
Control platform: Rinnai PC board with digital controller display. Source manual: 100000467 (rev. 07 on rinnai.ca) (2020–2021).
Why a code is not a diagnosis
The code reports that recirculation flow is below what the control expects. The manual's checks cover the configuration (bypass plug out and filter in for crossover mode), the filters (inlet and bypass screens fouled), the settings (parameters for recirculation), the pump supply, and air trapped in the return line. Any of these can produce the same code.
Same code, other equipment
- Rinnai non-SENSEI series: Same code family per troubleshooting document 100000652. Source
Safe things to observe
- Note whether the fault appeared after recirculation was newly configured or after a filter cleaning interval.
- Check whether hot water still arrives normally at taps outside the recirculation loop.
Do not
- Do not remove the bypass plug or run crossover mode without the bypass filter in place.
- Do not adjust recirculation parameters without the manual's procedure.
How professional service helps
- A technician verifies the bypass plug and filter configuration, cleans the inlet and bypass filters, confirms the recirculation parameter settings and pump supply, and bleeds air from the return line per the manual.
Diagnostic visit
Repair visits carry a diagnostic service fee that CANRO states is credited toward the repair if you proceed. The amount is confirmed by phone; it is not published. Source, checked September 7, 2026.
Where CANRO provides on-site service
On-site service is currently offered across Metro Vancouver: Vancouver, Burnaby, Richmond, Surrey, Coquitlam, North Vancouver, West Vancouver, New Westminster, Delta, Langley, Port Moody, Port Coquitlam, Maple Ridge, Pitt Meadows, White Rock, Tsawwassen; plus Anmore, Belcarra, Lions Bay, Bowen Island, Abbotsford with travel or ferry arrangements confirmed by phone. Everything else on this site is reference information you can use anywhere in Canada.
Frequently asked questions
What is the bypass plug and filter for?
In crossover-valve recirculation mode, a bypass fitting at the far fixture lets hot water loop back through the cold line; the plug must be removed and the bypass filter installed for the control to see the flow it expects.
Can a dirty inlet filter cause code 63?
Yes. The manual lists both the inlet water filter and the bypass filter; fouled screens reduce flow and trigger the low-flow report.
Locked out with no hot water? Call with the code ready.
The brand, model and this code are passed along when you request service online, so the technician arrives prepared.
On-site service in Metro Vancouver, BC. Call to check availability.
Sources and verification
- Rinnai RU series Installation and Operation Manual, section 5.6 Diagnostic Codes · 100000467 · accessed September 7, 2026
Facts checked September 7, 2026. Last updated September 7, 2026. Technical reviewer: not yet assigned.