A Step-by-Step Guide to Changing a Radiator Valve

Radiator valves don’t last a lifetime and updating an old manual radiator valve to a new thermostatic valve can help to make your heating more efficient. With the potential to help lower your heating bills a thermostatic valve could save you hundreds!

Keep reading to find out how to replace a radiator valve step by step.

Why change a radiator valve?

Two of the main reasons for changing a radiator valve are likely to be due to an old or broken valve or if you want to change a manual radiator valve to a thermostatic radiator valve (TRV). If you are unsure about the replacement process, we advise consulting a professional.

What is a TRV?

A thermostatic radiator valve simply put is an upgraded version of a standard radiator valve. Where standard radiator valves only allow you to either turn the radiator on or off, a TRV allows you to control the temperature of the room.

A thermostatic radiator valve has a numbered dial which can be turned up or down in increments depending on how warm you need the room to be. This also allows you to control the temperature of each room in your home. For example, in rooms that you use all the time, you might have your TRV set to the highest number but in spaces such as a spare room or utility room, you may have it turned down to the lowest setting.

This type of valve is also able to detect changes in temperature, for example, if you have your thermostat set to 18 degrees, and a TRV senses the room is at 18 degrees it will prevent it from getting any warmer.

TRV’s however, shouldn’t be used on a radiator in the same room as a room thermostat as they both work in the same way to turn the heating off when it reaches your desired temperature.

Types of TRV

Thermostatic radiator valves are available in two different shapes, straight or angled. It is essential to check which type of valve you currently have as straight, and angled radiator valves aren’t interchangeable.

A straight radiator valve will have two connections at the bottom of the head whereas an angled radiator valve has one connection at the bottom and one on the side of the valve.

What you will need:

  • New thermostatic radiator valve (make sure you have the correct angle: straight or angled)
  • Adjustable spanner
  • Pair of grips
  • Radiator key or screwdriver
  • Old towels or sheets (collect any excess water)
  • Wet & dry vacuum or large container (collect any excess water)
  • PTFE tape (might need if the valve doesn’t reseal)

Turn off central heating

The first thing to do is to make sure to turn your central heating off. Before changing your valve make sure that the radiator has had time to completely cool down, to prevent burning yourself.

Prepare the area

Before you remove the valve prepare the area by putting down old towels underneath your radiator and keeping a bucket or container close by to catch any excess water.

Close your lockshield valve

First, you need to locate your radiator's lockshield valve. This is located towards the bottom of your radiator.

To close the lockshield valve you need to remove the cap with your adjustable spanner. Once you’ve removed the cap, you’ll have access to the valve itself. Use your adjustable spanner to turn the valve anticlockwise until you feel it comes to a stop. It’s a good idea to make a note of the amount of turns you had to make so you know how far to turn the valve when opening it again later.

Remove the old valve

Once you have closed the lockshield valve you now need to locate the existing manual radiator valve, which can be found towards the bottom of your radiator where it connects to the pipework. Loosen the bottom nut with your adjustable spanner making sure any slight water leakages are caught in your container of bucket.

Next, supporting the valve with grips you need to need to fully loosen the top nut. Once you have done this make sure you have your new valve to hand, with the decorator cap still attached.

You can now fully remove the bottom nut and carefully remove the valve. Be aware this is likely to result in quite a bit of water loss, so keep your tub at hand to catch the water.

Fit the new valve

You can now insert your new valve and tighten the nuts. When tightening the nuts, it’s best to use your grips to support the valve and prevent damaging the pipework.

Now’s the time to remove the decorator cap but make sure to keep it safe as you might need it again in the future, especially if you ever need to take the radiator off the wall to decorate behind it.

With the TRV head fully open you can now reattach this to the valve. Simply push the head into the top of the valve and tighten the collar by hand. Your next task is to re-open the lockshield valve, again using your adjustable spanner, this time turning the valve clockwise, the same number of times you turned the valve when closing the valve.

Bleed the radiator

Once you have completed the above and your new thermostatic radiator valve is fitted, you’ll need to bleed the radiator. To bleed your radiator, you’ll need a jug or bucket to collect any excess water and your radiator key or screwdriver.

Make sure you have your jug positioned under the bleed valve then simply turn the valve anticlockwise with your radiator key or screwdriver until air starts to escape and you hear a hissing noise. This is when you will get some water leakage. You can now turn the valve clockwise with your radiator key to tighten it again. You have now finished bleeding the radiator.

Please note:

  • If you don’t drain the system you don’t need to replace the inhibitor.
  • Don’t forget to save your radiator valve caps. These might come in handy later down the line if you need to seal the radiator without your TRV valve. For example, if you need to remove your radiator to paint the wall behind.

If you're looking for further information on radiators and heating, take a look at the following posts - How to Paint Behind Your Radiator - Single vs. Double Radiators: Which One Do You Need? - Choosing the Best Radiator for Your Home.

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