If your radiators are not heating evenly or you notice cold patches at the top, this often means air has become trapped inside the system. At Proper Heat, we know how frustrating this can be, especially when you are relying on your heating to keep the house comfortable. The good news is that bleeding a radiator is a quick and simple task that most homeowners can do themselves. Here we explain how.
Always begin by switching off your heating system and allowing it to cool. This is an essential safety step because radiators can hold very hot water, and opening a valve while the system is on can cause scalds or leaks. Waiting until the radiators are cool also ensures that any trapped air escapes more steadily.
Each radiator has a bleed valve, normally found at the very top corner. It looks like a small square pin or a slotted screw head. Before opening the valve, place an old towel or cloth beneath it, and position a small bowl or jug underneath to catch any water that may escape. Taking this precaution helps you avoid mess and protects flooring or carpets.
To open the valve, you will need a radiator key. These are inexpensive and available at most DIY shops if you do not already have one. Fit the key snugly onto the valve. In some modern radiators, a flat-head screwdriver may also work, but a radiator key is usually the most reliable option.
Turn the radiator key gently anti clockwise. You will hear a hissing noise, which is the sound of trapped air escaping. Hold the key steady and keep your bowl or towel ready to catch any drips. Be patient and let the air release at its own pace. Do not force the valve open too much, as it only needs a slight turn.
When the hissing stops and a thin stream of water begins to come out, it means the air has been fully released. Allow just enough water to run so you are sure the radiator is filled. Then quickly prepare to close the valve before too much water escapes.
Turn the key clockwise to tighten the valve again. Make sure it is secure but avoid overtightening, as this can damage the valve. Use your towel to wipe away any moisture and ensure the valve is completely closed.
Go through your home and repeat this process for any radiators that feel cool at the top or are making gurgling sounds. Start with the radiator furthest from the boiler and work your way closer. This helps the system balance itself more effectively.
Once all the radiators have been bled, switch the heating system back on. Walk around your home and check that each radiator now warms evenly from top to bottom. If you notice one still has cold patches, it may need to be bled again, or there could be another issue such as sludge build-up.
After bleeding radiators, it is common for your boiler pressure to drop slightly. Look at the pressure gauge on the boiler display. Ideally, it should sit between 1 and 2 bars when the system is cool. If it is below this level, you may need to top up the pressure using the filling loop, which is explained in your boiler manual. If you are unsure how to do this safely, get in touch with our team and we can guide you or arrange a visit.
Once you’ve bled your radiators, it’s always worth checking your boiler’s pressure gauge. Sometimes the pressure may drop slightly, and you may need to top it up. This is a straightforward process but if you’re unsure, you can contact us and we’ll guide you.
If your radiators still fail to heat evenly after bleeding, or you find you need to do it repeatedly, there could be an underlying issue. Common causes include sludge in the system, a failing pump, or even a boiler fault. That’s where our Gas Safe registered heating engineers can step in. We offer professional boiler repairs, installations, and servicing across Guildford and Godalming to keep your system running reliably.
Need help with your heating system in Guildford or Godalming? Proper Heat is here to help with boiler repairs, new installations, and routine servicing. Call us today or fill out our contact form to arrange a visit from one of our experienced engineers.
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