Takagi Condensing Code 441
Flow sensor fault. The flow sensor is not reporting correctly. It is what tells the heater water is moving, and a tankless unit will not fire without it — so this often presents simply as no hot water.
Part replacementThe verdict
Replace a part
A moderate part with a clear diagnosis. Before it is condemned a technician will check that debris is not stopping the turbine spinning, which is what the inlet filter exists to prevent.
Typical cost: $150–$500
US estimate for parts and labor. Prices vary by region and by who does the work — see how we estimate costs.
What the manual says
The meaning above is transcribed from the manufacturer's diagnostic documentation for the Condensing — not averaged across the brand.
Source: Takagi Condensing Models On-Demand Water Heater Troubleshooting Guide (p. 13), read Aug 2026 — the manufacturer's own documentation for this exact series.
What you can safely check
- Note whether the heater fires at all, and at which taps.
- Book a service call.
Frequently asked questions
Could a clogged filter cause this?
It is how flow sensors get damaged: debris that gets past a torn or missing inlet filter jams the turbine. Cleaning the filter afterwards will not clear the code, but it is why the sensor failed.
Code 441 on other Takagi series
Code 441 is a different fault on every other Takagi series that documents it, which is exactly why this page is written for the Condensing alone: