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How to Bleed a Radiator - The Simple Way

Welcome to the Only Radiators blog, where this week we reveal how to bleed a radiator with the least fuss and mess.

It’s always fun when you do your own maintenance – from putting the chain back on your bike to solving your computer problems, there’s no feeling of satisfaction quite like conducting some proper DIY and sidestepping the need to call an expert in.

Bleeding your radiator is one such task that may seem daunting but is actually incredibly simple. Stick with us as we take you through the process of how to bleed radiators.


Why Bleed Radiators?

Radiators, like any system running some form of liquid through them, are susceptible to internal build-ups that affect the performance of the system. This will only increase over time.

When we bleed our radiators, we are letting out air that has become trapped inside. This trapped air causes cold spots within the radiator, reducing their efficiency.

When you bleed your radiators, you improve the performance of your radiator. It takes less energy for your radiators to achieve your desired heat, which in turn makes for lower energy bills, and enables you to gain a warmer home for cheaper.


How Often Should I Bleed My Radiators?

Bleeding radiators should not be done too often as there is simply no need. And yes, many go for decades without ever bleeding their radiators and never experience any significant alteration in performance.

At Only Radiators, we recommend you bleed your radiators once every 12 months. The best time to do this is in the autumn, when conceivably – give or take a couple months depending on how tricky our indecisive weather is acting – you will be needing your radiators to wake back up and start performing as winter approaches.

So, time to answer the question on everyone’s mind – how do you bleed a radiator?


How to Bleed a Radiator

The first thing to say is that you’ll be pleased to hear bleeding a radiator is nowhere near as hard or deadly as it sounds. However, it can be every bit as messy as it sounds.

Follow these simple steps to make sure that bleeding your radiators is a quick, easy and clean process.

To bleed a radiator, you will need:

1 x radiator key/flat screwdriver

2 x rags

1 x container for collecting water

If you do not have a radiator key, you may be able to use a large flat screwdriver instead. Make sure before bleeding that the screwdriver can fit the valve snugly without rounding off the valve. This would make maintenance upon the radiator far more difficult to conduct in future.


  1. Diagnose

If your radiator is taking too long to heat up, or you can feel cold patches across the radiator (usually at the top depending on the position of piping) then you probably need to bleed the radiator. These cold patches are caused by trapped air or gas.

  1. Isolate

Turn your heating fully on and allow your radiators time to reach full heat. Your radiators must be hot before bleeding to build up the pressure inside them.

Now, you can assess each radiator for the above characteristics and figure out which radiators need bleeding.

WARNING: We know it’s obvious but we are required to remind you that radiators can get very, very hot –  so please be careful when checking them!


  1. Heating Off

It is very important that you turn the heating off once you have isolated the radiators that require bleeding. If you do not do this, you will end up with a lot of water on the floor and may potentially flood your home.


  1. Release Air

Now you will take your radiator key and fit it to the valve at the top of the radiator. Wrap one rag around the key to protect your hands from escaping hot air. Hold the other rag below the valve to catch any water that drips out and position your container underneath this for extra spillage.

Twist the key slowly anticlockwise to release air. You should be able to hear the air or gas escaping.

  1. Close Valve

When you can no longer hear air escaping from the radiator valve, the excess air has been released from the radiator.

This means that water within the radiator is quickly approaching the valve. Now quickly turn the valve clockwise before water floods out of your radiator.

Be careful not to over-tighten your radiator bleed valve as this may damage your radiator.

Also, keep in mind that modern screwdriver escape valves usually produce a far more violent ejection of water than older radiator valves – if so, be extra careful to use rags to prevent any spillage.

And that’s it! You have successfully bled your first radiator. Now, onto the others!


  1. Check Pressure

Check the pressure gauge on your boiler against recommended amounts. If it is too low after bleeding then you will need to top it up. You can add to your boiler pressure by adding water using the filling loop.

Make sure you always refer to the official instructions from your boiler manufacturer. If you are not sure how to do anything, ensure you seek professional assistance.

  1. Test Run

Now that you’ve bled your radiators, make sure they are all working properly with a hot test run. Turn on your heating, wait for your radiators to power up, and check that all previous cold spots have now gone.


  1. Persistent Cold

If any cold spots persist, first simply turn off the heating and repeat the above process.

You may not have fully bled the radiator in question of trapped air. It is common to have to perform the bleeding process a couple of times before your whole home heating system is back to full functionality.

If cold spots remain after repeat bleeds have been made, it is possible that you have a build-up of rust (also known affectionately in the home heating industry as ‘sludge’). If this is the case, you will need to get in touch with a qualified engineer to remove this build-up or follow our guide on how to flush sludge from your radiators if you feel up to the task yourself.

Well done – you have now successfully bled your radiators!


Automatic Radiator Valves

Technology is an incredible thing and is advancing at a ridiculous rate. The introduction of automatic radiator valves means you may now be able to bleed your radiators automatically.

The automatic radiator bleeder fits to your valve to gradually release trapped air from your radiator. This means there is no significant build-up of air and makes your boiler’s job far simpler.

If you’d like to find out about automatic radiator valves, give our team a call and we’ll be delighted to fill you in.


Other Ways to Improve Radiator Performance

Bleeding your radiators is the simplest, cheapest and most direct step to improving radiator performance. However, here are a few other cheap and simple ways to improve radiator functionality.


Radiator Insulation Foil

This ingenious product is laid across the wall behind your radiators and works by reflecting heat from the rear of the radiator back into the room.

We love this stuff here at Only Radiators – you can find it at almost any hardware store and it will drastically improve the heating of your home without having to change your home heating system at all.

Radiator Booster

You can also use a radiator booster, which is basically an elongated fan that sits atop your radiator and aids the circulation of warm air.

Aside from that, your best bet is insulating thinner-walled areas of your rooms or improving existing heating.


Start Bleeding, Stop Spending (So Much)

The facts are simple – over half of the bills we pay go toward heating and hot water.

Learning how to bleed a radiator will significantly reduce the amount of money you spend in this respect.

Before we go, we have one parting tip. Though it may seem like the obvious solution to minimising bills, it’s not all about keeping boiler activity as low as possible.

In the height of summer, it pays to switch your boiler on for 30 minutes every month. This will keep water pumping around the system and help to prevent the costly build-ups that can occur in long periods of inactivity. An annual boiler service can also help to prevent issues!


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As always, keep checking up on the Only Radiators blog time and time again for industry-leading home heating ideas, and sign up to our newsletter for exclusive news, money-saving tips, competitions and much more!

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