Why does the new one still weep?

Almost always the expansion vessel — check pre-charge first before condemning the PRV.

Only fit WRAS-approved 3-bar PRVs to keep Vaillant ecoTEC Plus 428 within its Gas Safe commissioning envelope.

Do I need to notify the manufacturer?

Only if the Vaillant ecoTEC Plus 428 is in warranty — Vaillant require log of any part swap for labour claims.

Fit a new 3-bar PRV on Vaillant ecoTEC Plus 428 when water dribbles constantly from the outside discharge pipe.

Drain below the PRV, unscrew the old valve and fit new PTFE tape (10 turns clockwise).

On Vaillant ecoTEC Plus 428 the PRV sits on the hydraulic block — torque to 25 Nm to avoid cracking the plastic manifold.

Refill the Vaillant ecoTEC Plus 428 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.

Why does the new one still weep?: Almost always the expansion vessel — check pre-charge first before condemning the PRV.
Any WRAS approval?: Only fit WRAS-approved 3-bar PRVs to keep Vaillant ecoTEC Plus 428 within its Gas Safe commissioning envelope.
Do I need to notify the manufacturer?: Only if the Vaillant ecoTEC Plus 428 is in warranty — Vaillant require log of any part swap for labour claims.

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