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Page last updated on 22nd July 2025

A pair of hands holding a screwdriver to a radiator's bleed valve.

How to bleed a radiator

If your radiators aren’t getting hot enough, it might be time to bleed them. But what does that mean, and what’s the best way to bleed radiators? Let’s dive into how to bleed different types of radiators and how often you should be doing it.

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What's on this page?

What does bleeding radiators mean?
Do my radiators need bleeding?
How often to bleed radiators?
How to bleed radiators in your house?
How to bleed radiator without a valve?
What if bleeding radiators doesn’t solve my heating problem?

What does bleeding radiators mean?

If your radiator runs on hot water, the hot water travels through all the radiators in your home when the heating is on, warming them up. Sometimes, air can build up inside a radiator, preventing the water from moving freely. The result: a radiator that never seems to get hot enough, wasting energy and money.

By learning how to bleed a radiator, you’ll know how to deal with the problem yourself. Bleeding a radiator means releasing the air trapped inside it, allowing the water to circulate, so you can stay warm and comfortable when the heating’s on.

Do my radiators need bleeding?

Now that we’ve covered the basic concept of bleeding radiators, let’s get into how to tell if a radiator needs bleeding.

Is it taking longer than usual for your radiators to warm up?
Are you hearing rattling or gurgling noises from your radiators?
Is the radiator cool or cold at the top when the heating is on?

If the answer to any of these questions is ‘yes’, especially the last one, you’ll probably want to follow our guidance on how to bleed a radiator below. If only the bottom of the radiator is heating up, that can be a telltale sign of trapped air in the system.

It’s an obvious point, but it’s always worth checking: if the whole radiator is cold, not just the top, make sure the radiator is on! To turn on your radiator, adjust the radiator control valve often located at the bottom of the radiator.

If your radiator is hot at the top and cold at the bottom, your problem might be sludge or debris in the system, which can be flushed out by a professional.

How often to bleed radiators

Even if your radiators seem fine, it’s a good idea to get into the practice of bleeding them on a regular basis. By keeping your central heating system free of trapped air, you’ll make sure it’s working as efficiently as possible, saving you money on your heating bills.

How often should you bleed radiators, then? Bleed them once a year, when the weather’s getting colder, to get them in top condition for the winter. If you are having to bleed your radiators more than once a year, it would be worth reaching out to a local plumber for advice, as this could indicate a larger issue.

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How to bleed radiators in your house

While most radiators will need bleeding, some do not. For instance, electric radiators do not circulate hot water through the home and don’t trap air, so they don’t need to be bled.

For those that do need bleeding from time-to-time, here’s the basic method for how to bleed a radiator:

Turn off the heating.

Before bleeding, make sure the heating is off, and the radiators are cool. This is important. If you try to bleed a hot radiator, you could end up with burns from the escaping air and water.
Check your radiator's bleed valve.

To know what tool you’ll need, check your radiator’s bleed valve. This will be at the top of your radiator, often on the side. If you can see what looks like a small square screw head, you’ve found it!
Find the right tool.

If the head of the valve has a slot in the middle, you’ll be able to use a flathead screwdriver to turn it. Don’t turn it yet, though; you’re just making sure you have everything you need! If it’s just a square with no slot, you’ll need a radiator key, which you can get from a DIY shop.
Grab what you need.

Grab an old towel and cover up the floor underneath the radiator valve. Dirty water is going to escape from your radiator in the bleeding process, so you’ll need something to protect your floors. For extra protection, aim to capture the water in a small container, such as a plastic tub.
Turn the valve.

Okay, now it’s time to turn the valve. You might want to cover your hand with an old cloth while you’re doing this. Turn it slowly anticlockwise until you hear the hiss of air escaping.

Tighten it back up.

Wondering how long to bleed a radiator? Just wait until water starts coming out instead of air, then tighten the valve up again. Close it completely, but don’t over-tighten it, or it’ll be harder to bleed next time!
Check your boiler pressure.

After bleeding, check your boiler pressure. To check your boiler pressure, locate the pressure gauge dial on your boiler – this measures your boiler pressure in bars. The ideal pressure should be between 1-2 bars, on the higher end when the heating is on.

If your pressure is less than 1.0 bar when the heating is off, your boiler may need re-pressurising. For re-pressurising your boiler, or if you’re not sure about your boiler pressure, check your boiler’s instruction manual, or consult a professional.
Turn the heating back on.

Turn your heating back on. Now, your radiator should be working properly.

How to bleed radiator without a valve

Wondering how to bleed a central heating radiator without a bleed valve? This is a slightly unusual problem, and often the answer is just that the valve’s been overlooked.

Take another look at the top of your radiator. Has the valve been painted over? If there’s nothing easily visible, it could be on the side facing the wall, so feel around the back of the radiator for the valve.

If there’s no bleed valve to be found, it may be best to have a professional look at your radiators.

What if bleeding radiators doesn't solve my heating problem?

If you’re still having heating issues after bleeding your radiators, make sure that your boiler pressure hasn’t dropped.

If you’ve bled your radiators and your boiler pressure is normal, but they are still not working properly, it might be time to call in a professional to look at the issue.

If your central heating is in working order, though, you can check out our guide on the ideal temperature for your house.

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