UK trade guideBoiler Spares 5 min readUpdated 11 July 2026

How to Replace the Pressure Relief Valve on a Worcester Bosch Greenstar 8000 Life 35 (UK)

Step-by-step UK guide to replacing the 3-bar PRV on a Worcester Bosch Greenstar 8000 Life 35. Part numbers, torques, commissioning.

Worcester Bosch

The part

Fit a new 3-bar PRV on Worcester Bosch Greenstar 8000 Life 35 when water dribbles constantly from the outside discharge pipe.

Isolate safely

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

Fit and commission

On Worcester Bosch Greenstar 8000 Life 35 the PRV sits on the hydraulic block — torque to 25 Nm to avoid cracking the plastic manifold.

Recommission checklist

Refill the Worcester Bosch Greenstar 8000 Life 35 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

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 Worcester Bosch Greenstar 8000 Life 35 within its Gas Safe commissioning envelope.
Do I need to notify the manufacturer?
Only if the Worcester Bosch Greenstar 8000 Life 35 is in warranty — Worcester Bosch require log of any part swap for labour claims.
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