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How To Bleed Your Radiators

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Posted: Monday, January 25, 2016

Bleeding a radiator is a simple process that is often the solution to a number of radiator problems. In a nutshell, it basically involves opening one of the valves temporarily to let the air 'bleed' out, allowing your radiator to work as you would expect it to.

It’s easy to bleed your radiator yourself and it can save you an unnecessary visit from a plumber. Take a look at our guide to find out everything you need to know to get it done quickly!

Why Do You Bleed Radiators?

Most radiators will need bleeding during their lifetime. Air can often find its way into your heating system, either when you are having repairs or maintenance carried out, or just through day-to-day usage. Once trapped inside, the air can stop your radiators heating up to the best of their ability, making your energy usage less efficient.

Bleeding your radiators ensures your heating is functioning to the best of its ability and you aren’t wasting money on your energy bills.

Our Step-By-Step Guide to Bleeding A Radiator

  1. Turn on the central heating

    Allow your radiators to reach their maximum temperature. If you have a thermostatic radiator valve, simply turn it to the highest heat setting. If you have a manual valve, turn it anti-clockwise until it doesn’t move any further.

    Check to see if there are any radiators in your home that are taking longer to heat up than others and if any are making a gurgling noise. Once they are all heated, see if they have any cold spots - this usually occurs towards the top of the radiator.

  2. Turn the central heating off again

    Once all your radiators have fully heated up and you know which ones need bleeding, turn the central heating off again. Wait for them to cool down completely before proceeding to bleed them.

  3. Get your supplies together

    While your radiators cool down, get your supplies ready. You will need:

    • A radiator key or flat head screwdriver if your valve isn’t hand operated
    • A cloth to help you turn the key
    • An old towel that you don’t mind getting dirty
    • A bowl or tray to catch any water drips
  4. Locate the bleed valve on your first radiator

    The bleed valve will be at either the right or left side of your radiator. On modern cast iron radiators, it might be brass and hand operated. For most steel radiators, it will need a radiator key or screwdriver.

    Place your bowl at the end of the radiator under the bleed valve, ready to catch any drips or leaks.

  5. Open the bleed valve

    If using a radiator key, attach it to the bleed valve. If you're using a screwdriver, place the head into the groove of the screw.

    Then, turn the valve in an anticlockwise direction. Hold the cloth to both help you get a better grip and to stop any water spitting out at you. You don’t need to fully open the valve - just a quarter of a turn or so should be enough.

  6. Wait for the air to bleed out

    With the valve open, you should hear a hissing noise as the air is released. Once the air stops coming and water starts leaking out, close the valve again by turning clockwise as far as you can.

    Repeat this process for all radiators in your house.

  7. Turn the central heating back on

    When you’ve bled all the radiators, turn the central heating on and let them reach maximum temperature again. Check the heat to see whether any cold spots have been eliminated, making sure there are no leaks coming from the bleed valve - if there are, check you tightened it back up enough.

    If any of your radiators still seem cold, try repeating the process.

  8. Check the boiler pressure

    Take a look at the pressure gauge on your boiler and make sure it hasn’t dropped below the recommended level - usually between 1.5 and 2 bars for most domestic hot water systems. If the pressure looks too low, simply top up the boiler until it is back to its proper reading.

FAQs for Bleeding a Radiator

Still have questions about how to bleed a radiator? Read our FAQs for more information...

How Do I Know When My Radiator Needs Bleeding?

There are a few signs that would suggest your radiator is in need of bleeding, including:

  • Uneven heat - usually hot at the bottom but cold at the top
  • Taking longer than usual to heat up
  • A gurgling noise when heating up
  • The sound of pipes banging when you turn the central heating on
  • In extreme cases, the radiator isn’t getting hot at all

If you notice any of these signs, it’s a good idea to try bleeding your radiator first - if bleeding doesn’t help, there might be something else wrong with them.

How Long Do You Bleed a Radiator For?

As a general guide, most radiators need bleeding until the hissing sound of air escaping stops. At this point, water should be leaking out steadily, with no air bubbles or spitting. Exactly how long this takes depends on the size of your radiator - it could vary anywhere from a few seconds to a minute.

Do You Bleed All The Water From a Radiator?

A little bit of water should come out when you bleed your radiator, but you shouldn’t bleed all of the water away. The main purpose of bleeding your radiator is to release the air, so close the valve as soon as the water starts leaking without any bubbles.

What to Do If No Water Comes Out When Bleeding a Radiator?

If you have to bleed your cold radiator frequently and air is repeatedly coming out with no sign of water, there could be another issue with your radiator. If you are sure the boiler pressure isn’t too low, it could be that you need to balance your radiators. If this still doesn’t help, there could be a build up of sludge inside the radiator. Call a plumber for advice, or perhaps it is time to replace your radiator with a nice new one!

Which Radiators Should You Bleed First

You should bleed the ground floor first radiator first, starting with the one furthest away from the boiler and working backwards.

Can You Bleed a Radiator Without a Key?

Most of the time, you do need a radiator key. However, if you have lost yours, you can easily find a replacement at a DIY or hardware store.

Some radiator bleed valves can be turned with a flathead screwdriver, however a radiator key often makes the job much easier.

Can You Bleed a Radiator When the Heating is On?

No - you don’t want to risk any boiling water shooting out at you. It’ll also help you bleed the radiators most effectively, as the water inside will have settled.

Put your heating on at least a couple of hours before you plan on bleeding your radiators. This allows the pressure to build up inside them and gives you a chance to identify which radiators are a problem. Then, turn it off and wait until they are cooled down before beginning the bleeding process.

How Often Should You Bleed Your Radiators?

You should bleed your radiators as soon as you notice a problem with them. This ensures your heating system is running as efficiently as possible and you’re not wasting money on energy that isn’t turning into heat.

The first chilly day when you turn your central heating on is a good time to check they are all heating up properly and bleed them, so you are ready for the colder months ahead. A quick annual check is a good routine to get into.

Does Bleeding a Radiator Reduce Boiler Pressure?

Yes, bleeding your radiators can reduce boiler pressure as you have released some of the water out of the system. This is easily put right though - just top up the pressure again with the filling loop on your boiler.

If your boiler pressure has dropped after bleeding your radiators, return it to the recommended level (usually 1.5 to 2.0 bar), or you might find your radiators are still cold. If your boiler pressure looks ok and your radiators are still cold, try repeating the bleed process again for a second time.

Is it time you updated your radiators? Here at Trads, we have an excellent range of beautiful cast iron and steel radiators to update your home with!

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Feel free to contact us if you need any help choosing a radiator

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