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 Viessmann Vitodens 100-W 30 within its Gas Safe commissioning envelope.

Do I need to notify the manufacturer?

Only if the Viessmann Vitodens 100-W 30 is in warranty — Viessmann require log of any part swap for labour claims.

Fit a new 3-bar PRV on Viessmann Vitodens 100-W 30 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 Viessmann Vitodens 100-W 30 the PRV sits on the hydraulic block — torque to 25 Nm to avoid cracking the plastic manifold.

Refill the Viessmann Vitodens 100-W 30 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 Viessmann Vitodens 100-W 30 within its Gas Safe commissioning envelope.
Do I need to notify the manufacturer?: Only if the Viessmann Vitodens 100-W 30 is in warranty — Viessmann require log of any part swap for labour claims.

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