UK trade guideBoiler Spares 5 min readUpdated 11 July 2026

How to Replace the Pressure Relief Valve on a Glow-worm Energy 35c (UK)

Step-by-step UK guide to replacing the 3-bar PRV on a Glow-worm Energy 35c. Part numbers, torques, commissioning.

Glow-worm

The part

Fit a new 3-bar PRV on Glow-worm Energy 35c 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 Glow-worm Energy 35c the PRV sits on the hydraulic block — torque to 25 Nm to avoid cracking the plastic manifold.

Recommission checklist

Refill the Glow-worm Energy 35c 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 Glow-worm Energy 35c within its Gas Safe commissioning envelope.
Do I need to notify the manufacturer?
Only if the Glow-worm Energy 35c is in warranty — Glow-worm require log of any part swap for labour claims.
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