How to Replace a Boiler Pressure Relief Valve (UK)
Fit a new 3 bar PRV on Worcester, Vaillant, Baxi and Ideal boilers. Cures constant drip to the outside discharge.
Worcester BoschVaillantBaxiIdealCaleffi
Diagnose
A dripping outside discharge pipe is either a failed PRV (mineral scale on seat) or expansion vessel gone. Recharge vessel first — cheaper — before swapping PRV.
OEM part numbers
- Worcester Greenstar — 87161028420.
- Vaillant ecoTEC — 0020132681.
- Baxi 800 — 720030201.
- Ideal Logic — 173956.
Fit
Isolate, drain, unscrew (usually 22 mm compression on the discharge). New copper washer, torque hand-tight + 1/8 turn.
Frequently asked questions
- Can I plug a leaking discharge to stop the drip?
- Never. The discharge must be free — capping breaches Building Regs G3.
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