This guide will show you how to bleed a radiator in seven simple steps, helping you combat cold rads and improve your home’s heating efficiency.
When to bleed radiators
If your radiator is cold at the top but hot at the bottom, then there’s likely to be air trapped inside and you may need to bleed it. Here are some other tell-tale signs that your radiator needs bleeding:
Radiator cold at the top
This is the most common sign that your radiator needs bleeding, which essentially means air has collected in the radiator, stopping the hot water from circulating around and heating it up. The air needs to be released so your radiator can heat up effectively. Patchy warmth in your rad is definitely a sign it needs to be checked out before it stops heating up altogether.
Entire radiator is cold
Though this isn’t as common a sign that radiators have air trapped in them, it certainly is a sign that your radiator needs attention. Trapped air somewhere in the pipes has restricted the hot water which is meant to be flowing into the radiator – this can cause bigger problems later if it’s not sorted quickly! You should get in touch with your local heating engineer to get things toasty again.
Mould or damp around the house
If you’ve noticed grubby damp patches or mould sneaking in on the walls, particularly in rooms that aren’t used very often, this could be a sign your radiators need some attention.
Radiators are rattling
Trapped air in your heating system may cause your radiators to make funny noises, like gulping, gurgling and rattling. Whilst this could be for various reasons, it may be a sign that you need to bleed the radiator. Either way, your rad needs to get checked to make sure the problem isn’t more sinister.
What do I need to bleed my radiators?
You’ll need the following items to bleed a radiator:
- Radiator key
- Bucket or mug
- Safety Gloves
Warning: The water inside radiators can be very hot, so take care not to scold yourself (wear protective gloves and clothing) – you should also protect your floors!
Bleeding a radiator in 7 simple steps
Follow this simple step-by-step guide to check and bleed your radiators:
- Turn your heating on
Turn your heating on and wait for all of the radiators in your home to warm up (the length of time may depend on how many radiators you have and the size of your home, so be sure to give yourself plenty of time).
- Identify which radiators need bleeding
Carefully check each radiator to ensure it has an even temperature across the whole surface area. If you do find any radiators that are cold at the top or hear any gurgling noises, it’s a good indicator that there’s trapped air inside and that you’ll need to bleed it.
Tip: We recommend wearing a thin pair of gloves when checking each radiator as they may be very hot.
- Turn off your heating and wait for the radiators to cool
Before you start bleeding any radiators, we recommend turning off your heating so the radiators aren’t too hot to touch
- Place a cloth below the radiator bleed valve
Locate the radiator bleed valve and ensure that a cloth or an old towel is placed below it to catch any water that may be released.
Tip: Every radiator has a bleed valve. They’re typically located at the top corner of a radiator and look like a round hole with a square inside.
- Open the valve and release the air
If no water or air comes out when you bleed the radiator, then the valve could be blocked with paint. Close the inlet and outlet valve at each end of the radiator, then remove the screw from the centre of the bleed valve. Insert the radiator key into the bleed valve and slowly turn it anti-clockwise (a quarter of a turn should be enough). You should hear a hissing sound as the air escapes.
Tip: We recommend having a bucket handy to catch any spurting water, just in case you open the valve too far.
- Close the valve
Once the hissing sound stops and water starts to leak out, turn the key clockwise to close the valve.
- Check the boiler pressure
Repeat this process for each radiator that needs bleeding in your home. Once you’ve finished doing this, you’ll need to check the pressure of your boiler’s water pressure gauge.
If the boiler pressure is too low (below 1 bar), you’ll need to repressurise the system. If the pressure is normal (between 1 and 2 bars), you can switch your heating on and check that your radiators are now heating up as they should.
HomeServe’s top tips
How often should you bleed a radiator?
You should do a full check of the radiators in your home every couple of months. We recommend checking your radiators before the cold weather arrives, ensuring your heating system is running efficiently when you need it most.
Can you bleed a radiator when the heating is on?
You must not bleed a radiator when the heating is turned on as it may be too hot to touch and hot water could spray out of it. Ensure the heating is turned off before you begin bleeding a radiator. Letting out air when the pump is running will only draw more air into the system from elsewhere.
Can I use automatic radiator valves to bleed my radiators?
Depending on what type of radiators you have in your home, it may be possible to bleed them automatically using an auto vent. These handy devices are attached to your radiator valves and let out air gradually over time. Helping to keep your radiators working efficiently, with an auto vent you won’t need to bleed them manually.
How do I know if bleeding my radiators has worked?
Once you’ve closed your radiator valves, it’s safe to turn your central heating and hot water back on. If you’ve been successful, your radiators should start to heat up within a few minutes. You can also check the pressure gauge on your boiler and check that it reads between 1 and 2 bars.
Are your radiators still cold after bleeding them? For help diagnosing and fixing the issue, contact HomeServe and we’ll put you in touch with a fully qualified, Gas Safe registered heating engineer.