Takagi tankless water heater code 701
Your series decides which reading applies. Across the 2 Takagi series documented here, code 701 is listed as proportional valve or computer board fault (1 series) and computer board fault (1 series). Find your series in the table below, where those readings route to a professional.
What code 701 means on each Takagi series
| Series | What it means | Verdict | Typical cost |
|---|---|---|---|
| Condensing | Proportional valve or computer board fault | Call a pro | $400–$1,100 |
| Non-Condensing | Computer board fault | Call a pro | $400–$1,100 |
Each row opens the full page for that generation. We hold manuals for Condensing and Non-Condensing, and each one gets its own reading of code 701 — what Takagi documents, what you can safely check yourself, and what the repair should cost.
What each manual actually says
The table above compares 2 series in four columns, which is enough to route you and not enough to explain anything. This is the Takagi wording behind each row, one entry per manual, so you can see where the 2 readings of code 701 agree and where they part company.
Condensing — 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.
Non-Condensing — Computer board fault
The computer board itself. Worth noting the difference from the condensing range, where the same number covers the proportional valve **or** the computer board; here Takagi names the board alone. Shown as 70 on a T-K4 or T-KJr2 remote, or one flash of the red LED.
Does it matter which Takagi you have?
Condensing and Non-Condensing all route code 701 the same way: a professional, at $400–$1,100. That makes it one of the Takagi numbers you can act on before working out which unit you own.
What to check first, whatever your series
These checks are on the manufacturer's list for every Takagi series that reports code 701, so they are safe to work through before you have identified your exact unit. They also cost nothing.
- Turn the heater off and leave it off.
- Check whether the unit is still within its parts warranty.
- Book a licensed professional.
That is 3 of the 3 checks documented for code 701. The rest differ by generation, so if none of those explains it, go to your own series above.
Which Takagi do you have?
On the 2 series that report code 701, the model number on the rating label starts T — match yours against the 3 listed below. You can also use the full model-number decoder.
Where this comes from
Source: Takagi Condensing Models On-Demand Water Heater Troubleshooting Guide (p. 13), read Aug 2026 — the manufacturer's own documentation for this Takagi range.
Source: Takagi Non-Condensing Models On-Demand Water Heater Troubleshooting Guide (p. 12), read Aug 2026 — the manufacturer's own documentation for this Takagi range.
Parts, guides and symptoms behind code 701
Code 701 on these 2 Takagi series points at 2 parts and 1 symptom, each named by the manufacturer's own procedure for this code.