Takagi TK-1 Legacy Non-Condensing Tankless Water Heater
Takagi TK-1 Legacy Non-Condensing Tankless Water Heater Review
The Takagi TK-1 Legacy is a discontinued mid-tier non-condensing tankless water heater in the Takagi (now Rheem-owned) line. Replaced by current production Takagi T-K4 and T-H series. Legacy units remain in service in many homes installed 2005-2018.
Specs: 140,000 BTU natural gas input, UEF 0.82 (non-condensing), 6.9 GPM at a 35°F rise, copper heat exchanger, stainless steel B-vent venting. 10-year warranty on heat exchanger (original installation).
Service support: parts available through Rheem's network (Takagi acquired by Rheem in 2009) with the Takagi TK-1 model number used for identification. The unit is parts-supported through 2030 per Rheem's commitment.
For replacement, the current Takagi T-K4-IN-NG or Rheem RTGH series are direct replacements with similar specs.
Used TK-1 units appear in marketplaces at $400-$700 — substantially below new-unit pricing but without warranty transfer. For primary residence install, used purchase is high-risk; for vacation home with light use, used can be acceptable.
- On-demand operation at 7 GPM — no standby heat loss; unlimited hot water if demand is within flow-rate capacity
- 10-year warranty — solid above-average coverage for this class
- 7 GPM flow rate — sized for 2-bath simultaneous demand in warm-climate installs
- Requires dedicated 185K BTU gas supply line — undersized gas piping is the leading cause of flow-rate shortfalls