Radiator Bleed Valve

Radiator bleed valves. A very important and often overlooked part of your central heating system.

It is good practice to bleed your radiators annually and completely drain your system every 5 years or so making it very important that your bleed valves are in working order.

Here at Plumbing Wizard, we get asked a lot about radiator bleed valves. This is because they are not something that the average person will have in their home or apartment. The most common question we get is “How do I replace my radiator bleed valve?

Well, the answer is pretty straightforward, and in this article, we will tell you how.

What are Radiator Bleed Valves?

Radiator “bleed” valves are designed to “release” a small amount of air and/or water from the system in order to reduce the level inside.

They’re typically placed at the top of the radiator because any air that will be trapped inside will be forced upwards by the pressurised water below.

With most common radiator designs, at the top of each end, there will be a plug inserted – one of them will be blank (smooth finish) and the other will have some kind of opening or fitting that can be opened with a tool or key – this one is the bleed valve.

Why do Radiator Bleed Valves Need Replacing?

There are a number of reasons why you need or want to replace your bleed valve but don’t worry, it is not a difficult task so keep reading and we will cover that shortly.


One of the most common reasons for replacing a bleed valve is that the bleed valve has failed and is leaking.

A leaking bleed valve can cause havoc in the pressurised system and will need rectifying sooner rather than later. You could try removing the bleed plug and attempting to reseal but, in most cases, it is best to just buy a new one.


Another reason could be because the bleed valve has been painted over and doesn’t look very good and you want to have nice shiny fittings on your radiators.

Bleed valves that have been painted do not look very appealing and once the radiators have been bled again, the paint will have cracked which probably defeats the object of painting it in the first place.

Cannot Get a Good Seal

If you have had to remove the bleed plug for any reason, you may be struggling to get a good and watertight seal.

Bleed plugs can often be removed when a system needs draining or the radiator needs flushing and may be due to age, wear and tear or poor technique, you may end up struggling.

How to Replace Radiator Bleed Valves

Luckily, this is another one of those simple tasks that you can do without panicking and calling out a plumber to fix it for you. The parts are inexpensive too.

What You Need

  • New Radiator Plugs
  • Adjustable Spanner
  • Bleed Valve Key
  • Lockshield Valve Key
  • Towel/ Rag
  • Bucket
  • PTFE Tape

Step 1 – Turn Off the Heating

First, we need to turn off the heating system and let it cool. Inevitably there will be some water escaping when you replace the bleed valve, so it is best to make sure that the water is cold enough to touch.

Step 2 – Isolate the Radiator in Question

Next up, we need to isolate the radiator from the rest of the heating system. We can do this by turning off the valves at each end – the first is the TRV (the one you use to turn the radiator temperature up/ down), and the other is known as the lockshield valve which usually requires a tool or lockshield key to open/ close.

Note: Remember to note how far you turned the lockshield valve to close it. When you open it again, you want to ensure that it is opened to the same place, or you may need to rebalance the system.

Step 3 – Open the Bleed Valve

Now you will want to open the bleed valve. Make sure you have your bucket well-placed and your towel ready as there is likely to be some water escaping.

Keep the valve open until the water stops flowing out although if you are unable to open the bleed valve, move on to step 4.

Step 4 – Remove the Bleed Plug

Now you will need your adjustable spanner to remove the bleed plug (and the blank on the other end).

Note: If you were unable to open the bleed valve in step 3 – undo the plug slowly and be prepared for some water to escape.

Step 5 – Wrap Your New Plugs with PTFE Tape

This step is important to prevent leakage as new plugs alone will not be enough to prevent leakage so the threads will need to be wrapped. This is especially true when using new plugs on older radiators.

You will want to take your new plugs and wrap the PTFE tape around the threads, pressing the tape into the grooves as you go. How many times you wrap the thread will depend on the valve, but 3 times around is a good benchmark.

Now you will need to clean around openings and insert the plugs and do them up nice and tight letting the PTFE tape create the seal.

Step 6 – Turn on the System

Now you can add the radiator back to the system and turn it all back on. Remember to open the lockshield valve by the same amount that you closed it and turn on the TRV.

After removing the plugs there will be a bit of air in the system that should make it to the AAV although now would be a good time to make sure all of the radiators are bled.


As you can see, this is not a difficult task and no need for panic stations. The best thing to do is keep calm and carry on. The article above is aimed at replacing standard bleed valves located on most radiators.

If you have designer radiators and have different bleed plugs located somewhere else on your radiator, you may need to get replacement plugs from your manufacturer – don’t worry though, the process of changing them is still the same.

Plumbing Wizard Tips

“Always remember to bleed your radiators every year!”

“Do not forget the PTFE tape – without this, you will not get a watertight seal!”

“When closing the lockshield valve always note how much you turned it!”

“Make sure that you turn the heating off – the last thing you want is a trip to the hospital for scalding yourself!”

Frequently Asked Questions

Can you change a radiator bleed valve without draining the system?

Yes, you do not need to drain the whole system to remove and replace a bleed valve. This can be done by isolating the radiator in question by closing the TRV and lockshield valves.

Are all radiator bleed valves the same size?

No, all radiator bleed valves are not the same size. Although many radiators use a standard size, you may find that designer radiators will have a different design.

How do you remove a rounded radiator bleed valve?

If you are trying to remove a radiator bleed valve and the nut is rounded, you can try using some grips. Another good way would be to file 2 edges opposite each other so that you can get a good purchase with your adjustable spanner.

About Me

I’m Lee the Plumbing Wizard. I’ve been a plumber for over 40 years and have seen it all. People used to call me a magician because I could fix things so easily – hence the name Plumbing Wizard.
I’m always happy to help out a fellow tradesman or woman, so if you need any advice or just someone to talk plumbing with, don’t hesitate to get in touch!

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