Radiator Not Getting Hot – What to Do?

The most common cause is air trapped in the radiator, which prevents the hot water from circulating. Step 1: Turn the thermostatic valve up to its highest setting. Step 2: Locate the bleed valve (a small screw or nipple at the top side of the radiator). Step 3: Hold a cloth beneath it and slowly turn the valve anticlockwise using a radiator bleed key (approx. £2, available from DIY stores) until water flows out instead of air – then close it immediately. Step 4: Check the system water pressure afterwards (pressure gauge on the boiler: target value 1.5–2 bar). If the radiator is warm at the bottom but cold at the top, bleeding it usually resolves the issue. If it remains completely cold, the thermostatic valve may be faulty – this can be replaced inexpensively as a DIY job.