Lockshield Valve
Also known as: radiator lockshield, balancing valve, return valve
The capped valve on the return side of every radiator. Its main purpose is to balance the heating system so each radiator gets the correct flow — it is set by an engineer and then locked in position.
On the opposite side of the radiator to the TRV, covered by a plastic cap (often blue or white).
Chrome or white valve with a removable plastic cap. Underneath the cap is a slotted spindle adjusted with a spanner — not a screwdriver.
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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.