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✅ HelpfulValves & Stopcocks
The Lockshield Valve — Balancing Your Heating
Every radiator has two valves. The TRV on one side controls temperature. The lockshield on the other side has a plain plastic cap — and most homeowners never touch it. But it plays a crucial role in how evenly your home heats.
🔍 What it looks like
The lockshield has a plain plastic cap (often white or grey). Remove the cap and underneath is a small spindle you turn with an adjustable spanner. It's intentionally difficult to accidentally adjust.
⚙️ What it does
The lockshield controls how much hot water flows through the radiator. By partially closing lockshield valves on radiators nearest the boiler, more water flows to radiators further away. This is called balancing the system — and it's why some rooms are always too hot while others are cold.
🛠 What to tell an engineer
"My downstairs rooms get very hot but my bedroom radiators barely warm up — I think the system might need balancing." A heating engineer will adjust lockshield valves across all radiators. If a lockshield is completely closed, the radiator won't heat at all even with the TRV fully open.
Good to know: Radiator balancing is often overlooked. A balanced system is more comfortable, cheaper to run, and easier on the boiler.
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General guidance only — not a substitute for professional advice. Always consult a qualified engineer if you are unsure. Gas work must only be carried out by a Gas Safe registered engineer. Unvented (pressurised) hot water systems must be worked on by a G3-qualified engineer. We accept no liability for any loss, damage, or injury arising from the use of this information.
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