Pressure Relief Valve (PRV)
Also known as: safety valve, boiler PRV, pressure valve, discharge valve
A safety valve that automatically opens to release pressure if the system exceeds 3 bar. It is a critical safety device — if it keeps opening, the underlying pressure problem must be investigated.
On the boiler body or unvented cylinder, with a discharge pipe leading outside or to a tundish.
Brass valve with a red or yellow lever (test/lift lever), 15 mm or 22 mm connection. Discharges via a copper or plastic pipe.
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Always turn off the water supply before replacing any part. If in doubt, consult a qualified plumber. Gas components must only be worked on by a Gas Safe registered engineer. Unvented (pressurised) hot water systems must be worked on by a G3-qualified engineer. Prices shown are indicative — check retailers for current pricing.