What you'll need
A radiator bleed key (from any hardware shop, or a flat-head screwdriver on some modern radiators), an old towel or cloth, and a small container to catch drips.
Step-by-step
1. Turn the heating on and let radiators reach full heat, then turn it off and wait 10 minutes for water to stop moving.
2. Start with the radiator furthest from the boiler on the ground floor, then work upstairs.
3. Hold the cloth under the bleed valve and turn the key anti-clockwise about a quarter-turn — you'll hear a hiss.
4. When water starts to trickle out steadily, close the valve.
5. Check the pressure gauge on the boiler afterwards and top up to 1.2 bar via the filling loop if it's dropped.
When bleeding doesn't fix it
If radiators fill with air within days of being bled, or stay cold at the bottom while hot at the top, the system likely has sludge or a circulation problem. A power flush or magnetic filter fit resolves this — book a diagnostic visit.
Radiators still cold after bleeding? Book a heating diagnostic in KT/TW.
Call 07932 898534Frequently asked questions
How often should I bleed my radiators?
Once a year, ideally before winter. Bleed sooner if any radiator has cold spots at the top.
Do I need to turn the heating off before bleeding?
Yes — bleeding a live system sprays hot water and doesn't release air properly. Turn off, wait for water to stop moving, then bleed.
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