How to change a radiator valve


Whether your valve is faulty or you want to update your home, changing your radiator valves is a great way to upgrade decor and improve the energy efficiency of your central heating. Radiator valves are a crucial part of our heating systems, so they must work correctly and as efficiently as possible.

Changing a radiator valve doesn't need to be complicated. Find out how to change a radiator valve safely with our guide at PlumbNation.

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Types of radiator valves

There are several types of radiator valves available for you to choose from. Every home is different, which is why it helps to know the differences.

Angled radiator valve

As the name suggests, these valves sit at a 90-degree angle and are very common. They work with floor and wall pipework and are an excellent choice for modern homes which feature concealed pipework.

Corner radiator valve

The top of a corner radiator valve faces inward and sits parallel with the wall, rather than outward like an angled radiator valve. These valves are sometimes called flat front valves and are a great stylish option. Remember that this type of valve can be harder to adjust.

H-block valve

H-block valves work best on central connection radiators as they are easier to install and fit. This valve type is subtle and sits comfortably beneath a radiator, making them an excellent option for heated towel rails.

Manual valves

Most radiators in the UK will have a manual radiator valve as they are easy to use. They work by letting water in and out of the radiator to heat a room. However, manual valves can cause high heating bills if you don't use your central heating system on a timer.

Thermostatic radiator valve

Thermostatic radiator valves are great for improving energy efficiency and provide more control over room temperature. Depending on how warm or cool a room is, they turn themselves on and off, making sure your heating only ever kicks in when you need it most.

Straight radiator valve

This style of radiator valve is a good match if your piping runs along the wall, but they also work on pipes that join your radiator from the floor. Water in straight radiator valves flows straight through instead of at an angle.

Before you start

Make sure you have access to all the equipment you need before starting to change a radiator valve. Some of the items and plumbing tools you'll need include:

  • New radiator valves
  • A towel or old rags
  • Adjustable spanner
  • Small container
  • Radiator bleed key (flat top screwdriver will also work)
  • Grips
  • PTFE tape

1. Turn off the heating system

The very first step in changing a radiator valve is to shut off the heating system and water. Make sure your radiators cool down correctly if they've been on, and then turn off the lockshield valve to stop water from getting into that side of the radiator. Use an adjustable spanner to turn it clockwise and note how many turns it takes.

Next, turn the other valve off. If you have a manual valve, turn this clockwise until it no longer turns. For thermostatic valves, simply turn the dial to zero.

2. Drain the system

Depending on how many valves you're changing, you might need to drain the central heating system. To do this, find the drain off point from your boiler, which is usually at the system's lowest point. Turn off your radiators and combi boiler to prevent it from starting up.

Attach a hose to your drain off and run this outside into a drain. Once done, you can open the system drain cock, and let it drain completely. Go round all your radiators and open all the bleed valves. This prevents any further water from entering the radiators, allowing them to drain.

It typically takes around 10 or 15 minutes for a system to drain but will depend on the size of the system.

3. Remove the old radiator valve

The next step is to remove the old radiator valves. Protect your flooring from leaking water by placing a towel underneath the radiator and have a small container at the ready. Loosen the top cap nut on the radiator valve you're removing, but don't completely undo it. Listen out for a click when turning them, as this will tell you when to stop.

Use your pair of grips to hold the valve body in place and loosen the bottom nut. Doing this should allow you to remove the old valve. If your current nuts and olives are compatible with your new valve, leave them in place to make installing the new valve even easier.

Once the old valve is off, spend time cleaning the pipes. Use an old cloth to wipe over where the old valve was and clean up the pipework. It's a good idea to add some jointing compound to the radiator olives, as this creates a tighter seal for the new valve.

4. Attach the new radiator valve

Find your new radiator valve and grips. Double-check the arrows on your valve to see which direction the water should flow. Most modern valves have arrows pointing in both directions, showing the water flows both ways. If the valve only has one arrow, this will show the water flow moving into the radiator.

Use the grips to hold the valve body and align this with the pipework and radiator. Be patient, as this step can be tricky. Use your hands at first to tighten both cap nuts. Once you're happy the valve is in the right place, find your spanner and tighten the cap nuts until they're tight.

Once done, you can install the TRV head if a TRV is being fitted. The valve head should screw into the top of the valve by hand.

5. Remove and replace the lockshield valve

You don't need to replace the lockshield valve. However, if you want to match it with your new valve, now is a perfect time. To remove the valve, follow a similar process to step 4 above. Use your grips to hold the valve body in place and loosen and unscrew the top cap. Place your container under the valve to catch any excess water.

Once done, loosen and unscrew the bottom cap. From here, you can lift out the old lockshield valve. Use grips to align the new lockshield valve and connect it to the copper pipe and radiator inlet. Tighten up the top and bottom caps to finish the installation.

6. Open the valves and turn the water supply on

The final stage is to reopen the valves and turn your water supply back on. Make sure you've tightened the nuts and are happy the valve is secure. Go to each radiator and close the radiator bleed valve, and close any open valves. It only takes one open valve to cause water to leak onto the floor.

Go to your drain off point, remove the hose and close the drain off cock. Turn the water supply back on and allow the system to refill. At this stage, you need to check your radiators for leaking. If everything is okay, go to your new valves and open them to allow water to flow into the radiator. Check again for leaks and, if there aren't any, you're ready to enjoy your new valves.

7. Bleed the radiators and check the system

It's important to bleed your radiators after you've drained the system to let any trapped air out. If air has become trapped, this can stop water from adequately filling your radiators. Once bleeding is complete, turn on your boiler and let the radiators heat up. After an hour or so, check the valves once again to ensure there are no leaks.

Radiator Bleeding

FAQs about radiator valves

Do I need to drain the heating system to change a radiator valve?

It depends on how many radiator valves are being changed at once. If only one radiator is updated, you can probably do it without draining the entire central heating system. However, if more radiators and valves are being changed, it's best to drain the system completely.

Why do you need to change the radiator valves?

There are many reasons why you might need to change the valves on your radiator. For example, faulty radiator valves need replacing to stop any issues with your heating system, as they may become stuck or start leaking.

Updating your radiator valves from manual valves to thermostatic radiator valves is another common reason. TRVs are great for lowering energy bills, improving energy efficiency, and giving you more control over your heating.

Another reason why you might change your valves is to improve the look of your home. Adding more stylish valves can enhance the decor of a room and add value.

How does a thermostatic radiator valve (TRV) work?

TRVs or thermostat radiator valves are popular radiator valves as they help conserve more energy than a manual valve. These valves make it easy for you to change the temperature of each radiator and easily adjust them if a room doesn't need as much heating.

A sensor in the valve will automatically turn the radiator on or off to get to your desired temperature. A pin sits in the valve body and will open or close to control the flow of heating. Less hot water is used as the room warms up, and more is used as the room cools.

The two main types of TRV are wax and liquid-based. The liquid models are more popular as they are faster to react to temperature changes.

How do I check my new valve is the right size for my radiator?

It's important to make sure your new valves match the current pipework in place, as you won't be changing this. The best way to know if you've bought the right size is to measure your existing pipework and buy your valve to match this.

The size of your valve will depend on the valve connection size you have and not the design. Most copper piping is usually 15mm, but you should check to see the exact size of the connection. Your piping size will depend on the age and style of the home, with pipes measuring anywhere between 8mm and 28mm.

Is it easy to change a radiator valve yourself?

As long as you feel confident working with your radiators, changing a radiator valve is relatively straightforward if your heating uses a combi boiler system.

Although, if you do not feel confident, it's best to use a plumber, especially if you want to change a radiator valve without draining the whole heating system. It's trickier to work with conventional heating systems, so use a heating engineer if you have one of these.

For more advice on how to fit and change a radiator or need guidance on radiator valves, get in contact with our team at PlumbNation.