Radiator cold or leaking? What to check

If one radiator stays cold

• Check that both radiator valves are open and that a thermostatic valve head has not been left at its frost setting.
• If the top is cold but the bottom is warm, trapped air may be present. Only bleed it when the heating is off and the radiator has cooled, using the correct key and protecting the floor.
• If the bottom is cold while the top warms up, internal sludge or restricted circulation may be involved. Repeated bleeding will not remove sludge.
• If the complete radiator stays cold while others heat normally, a stuck valve, balancing issue or blockage may need professional investigation.

If several radiators are cold

Check the heating controls and whether the boiler or heat source is showing a fault before altering radiator valves. On a sealed system, low pressure can stop circulation, but repeatedly topping up pressure without finding the cause can hide a leak. Follow the manufacturer’s instructions and arrange qualified help for boiler or gas-related faults.

If the radiator or valve is leaking

• Turn the heating off and allow the radiator to cool. Keep water away from sockets, extension leads and appliances.
• Note whether the water is coming from the valve spindle, compression joint, bleed point, pipework or radiator body. A clear photograph helps with parts and planning.
• Do not keep tightening fittings. Excessive force can distort the valve or damage the pipe, turning a small seep into a larger leak.
• If water is escaping quickly or cannot be contained, treat it as urgent and isolate the appropriate system or main supply only if you know how to do so safely.

When a plumbing visit is sensible

Book a repair when a valve leaks, a radiator is loose, pipework is damaged, bleeding makes no improvement, or pressure repeatedly falls. AFS repairs and replaces suitable radiators, valves and connected heating pipework. Gas appliances and boiler faults must be handled by an appropriately qualified Gas Safe engineer.