How to Replace the Diverter Valve on a Baxi Duo-tec 40 GA (UK)
Step-by-step UK guide to replacing the 3-way diverter valve on a Baxi Duo-tec 40 GA. Part numbers, torques, commissioning.
The part
Replace the diverter valve on Baxi Duo-tec 40 GA when hot water runs cold on demand or the boiler cycles between CH and DHW.
Isolate safely
Drain to below the diverter body via the CH drain-off. On Baxi Duo-tec 40 GA the diverter is a cartridge design — pull the retaining clip and lift out.
Fit and commission
Fit new O-rings, silicone-grease the cartridge and align the actuator drive slot before refitting the motor.
Recommission checklist
Refill the Baxi Duo-tec 40 GA to 1.2 bar cold. Bleed high-point radiators and the internal AAV.
Run a full flue-gas analysis after 15 minutes. Log the reading against the OEM commissioning envelope in the Benchmark book.
Frequently asked questions
- Actuator or cartridge only?
- Diagnose first: manually push the actuator pin. If it moves freely, replace the actuator only; if the pin sticks, the cartridge is scaled.
- Any special tools?
- A brass spanner or the OEM diverter tool avoids cracking the plastic body on Baxi Duo-tec 40 GA.
- Do I need to notify the manufacturer?
- Only if the Baxi Duo-tec 40 GA is in warranty — Baxi require log of any part swap for labour claims.
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