Takagi Condensing Code 701
Proportional valve or computer board fault. Takagi pairs these in one code: the proportional gas valve — the part that varies gas flow rather than simply opening and closing — or the computer board that drives it.
Call a proThe verdict
Call a licensed plumber
Two possible outcomes at very different prices, which is why the diagnosis matters more than the guess. Both are professional work on a gas appliance; get the quote split into part and labour before agreeing to anything.
Typical cost: $400–$1,100
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
Before anything else: if you smell gas, stop here, leave, and call your gas utility.
- Turn the heater off and leave it off.
- Check whether the unit is still within its parts warranty.
- Book a licensed professional.
Frequently asked questions
Why does one code cover two very different parts?
Because from the board's point of view they fail the same way: the valve is not doing what it was told. Separating them takes measurements at the board, which is the first thing a technician does on this code.
Code 701 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
4 other Takagi 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: