Takagi Non-Condensing Code 651
Flow adjustment valve fault (Easy-Link systems). The flow adjustment valve, which meters how much water passes through the unit, is not behaving. Takagi marks this code Easy-Link system only on the non-condensing range.
Part replacementThe verdict
Replace a part
A moving part in the water path, moderate in price, replaced with the supplies off. Expect temperature that will not settle until it is done.
Typical cost: $200–$600
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 Non-Condensing — not averaged across the brand.
Source: Takagi Non-Condensing Models On-Demand Water Heater Troubleshooting Guide (p. 12), read Aug 2026 — the manufacturer's own documentation for this exact series.
What you can safely check
- Note whether the temperature swings and at what flow rates.
- Book a service call.
Frequently asked questions
Is there a bypass valve code too?
Not on this range. The condensing models have 661 for a water bypass valve; the non-condensing table has no equivalent.
Code 651 on other Takagi series
The same code number can mean something different on another series — make sure you're reading the page for your exact unit:
Don't confuse this with
2 other Takagi Non-Condensing codes point at a valve too. They are different components in different places, and ordering a part against the wrong one is the most common way this fault gets expensive: