How to change a radiator valve: a step-by-step guide

Have you found a fault with your radiator valve? Or perhaps you’re just redecorating, and fancy a change?

You’ve come to the right place. In this simple guide, we’ll show you exactly how to change a radiator valve.

What are the 2 valves on a radiator for?

Your radiator most likely has 2 valves, one on either side. They work a little like taps, and they look like small knobs that you can twist clockwise or anti-clockwise. 

One valve controls how much water can come into the radiator. The other controls how water is let out. Together, they control the temperature. Keep reading to find out how to tell which valve is which. 

Types of radiator valves: how do radiator valves work?

Manual or thermostatic radiator valves (TRVs)

The bigger valve is the one that controls how much water flows into your radiator – and so, how hot your room gets. 

The more basic variety are called manual valves. They usually look very simple, and using them is simple, too: you just turn them clockwise for on, and anti-clockwise for off. Very similar to a tap!

Thermostatic valves (see the photo below) are slightly more complex. Using these, you can turn the valve to your desired temperature for the room. Once the radiator has reached the temperature you asked for, it will stay there. (Unlike radiators with manual valves, which would get warmer until you turned them off.) 

TRVs can “sense” the temperature of your room, so they can warm things up if it gets cold, and put the brakes on before it gets too hot. 

Compared to manual valves, thermostatic valves are much more energy-efficient. 

Lockshield valves

The smaller valve on your radiator is known as the lockshield valve. This little part has the all-important job of keeping your radiator balanced, by letting out just the right amount of water. 

When a radiator is first fitted, the lockshield valve needs to be set. But once that’s done, you shouldn’t need to readjust it or fiddle with it any more. 

In the rest of this guide, we’ll be taking a closer look at how to change a manual or thermostatic valve.

What’s wrong with your radiator valve?: common radiator valve faults

You might need to change your radiator valve if you notice any of the following problems. 

• The valve is jammed, meaning you can’t turn it
• There’s a leak coming from your radiator valve
• Turning the valve has no effect on the radiator temperature
• Your radiator isn’t heating up properly

If you’re having problems with your radiator not getting hot enough, the valve might not be the culprit. Have a look at this guide to common boiler problems to rule out any other issues. It’s a good idea to try bleeding your radiators, too. 

When do you need to change your radiator valve?

There are 3 main reasons why you might want to replace your old radiator valve. 

1. It’s faulty. This is an obvious one – if your valve is stuck or failing to control your radiator’s heat, you’ll need a new one!
2. You’re swapping from a manual valve to a TRV. As we mentioned above, TRVs are far more energy-efficient than the older manual models. 
3. You just want something new! Perhaps you’re redecorating, and your old valves don’t match your new style. 

How often should you replace your radiator valves?

You don’t usually need to change your radiator valve unless there’s a problem, or you want to. 

Is it easy to change a radiator valve?

Yes! If you have a combi boiler, you can probably change a radiator valve yourself. Though if you’re unsure about anything, or you need to change multiple valves, it’s fine to call in an engineer, too. 

Got a system or conventional boiler, with a water tank in the attic? In that case, changing radiator valves might be more tricky. We’d recommend calling in an expert. 

But if you’re a confident DIYer, keep reading for a step-by-step guide. 

How long does it take?

It depends on your experience, but changing your radiator valve shouldn’t take more than an hour or 2.

How much does a new radiator valve cost?

A new radiator valve could cost as little as £10, if you opt for a basic model. Prices go up to around £30-£40 for better quality TRVs.

Is your new radiator valve the right size?

When you’re replacing a radiator valve, you need to make sure it will fit into your system. Make sure that the new one you’re buying is the exact same size as the one being replaced. Otherwise, it might not attach properly to your pipework. 

Ready to change your radiator valves? Here’s what you’ll need

• Your new valve
• An adjustable spanner or pliers, and a wrench
• Your radiator bleed key
• A hose
• A jubilee clip (to clamp your hose)
• Some wire wool for cleaning your pipes
• A dry towel or old sheets for the mess
• Jointing compound (a kind of grout)
• PTFE tape, if you want it, for extra protection against leaks

How to change a radiator valve in 7 steps

Remember, the following steps will work for you if you have a combi boiler system. If you have a system or conventional boiler, it might be a better idea to call a professional. 

Not sure? Find out what type of boiler you have. 

1. Turn off the heating and water supply

So, you’ve got all your equipment laid out beside you, and you’re ready to get to work. First things first: make sure your heating and water supply are totally switched off. This will prevent any injuries or unexpected messes.

Make sure your thermostats are turned to 0, and there’s no chance of the system starting up while you’re working. 

2. Put down towels or cloths

Things could get a bit messy, so at this point you should lay down some towels or old rags to protect your flooring. Put these under your radiator and surrounding pipes. 

At this point, you should also prepare your valves. If you’re changing a TRV, this means taking the heads off both valves, old and new. 

Take the nuts and connectors off the new valve, so that it’s ready to be fixed to the radiator. And coat the parts that will be connected to the radiator with your jointing compound. You might also want to wrap your PTFE tape around the connector about 8 times. This helps stop pesky leaks! 

3. Drain your system

Before you fit the new valve, you want your radiators to be emptied of water, and full of air. To do this, you’ll need to find your drain-off valve. This is likely to be underneath one of your downstairs radiators (it’s usually at the lowest point in the house).

Attach your hose to the drain-off with a jubilee clip. Then, put the other end of the hose outside. (You’ll also want to put a towel down underneath this part!)

Next, go around your house and use your radiator bleed key to bleed all of your radiators. Read our complete guide to bleeding radiators for a refresher on how to do this. 

4. Remove the old radiator valve

Once the water has been drained out of your heating system, it’s time to take off the old valve.

Hold the body of the valve with your wrench, while using your spanner to undo the top and bottom nut of the valve, by turning them anti-clockwise. As it loosens, take the valve off the radiator, and use your wire wool to clean up the pipes. 

Sometimes, your new valve might have different size cap nuts to the one you’re removing. In this case, you might have to remove the olives, too – these are small round pipe fittings that look like rings. You can usually unscrew them by hand, or use a hacksaw and screwdriver to take them off the pipes. 

5. Fit the new valve

Now for the crucial part! Simply put your radiator valve replacement where the old valve was on your radiator. Make sure it’s aligned with the water pipe and the radiator tail. 

As before, hold onto the body of the valve with your wrench, while tightening the nuts with your spanner. 

Be careful not to tighten the valve connections too much, or too fast. This could cause damage to your thread.

Finally, replace the top of the radiator valve that you removed earlier. Voila!

6. Turn the water back on and bleed the radiator again

Once your new valve is attached, it’s time to turn your water supply back on. First, make sure you’ve closed all the radiator bleed valves that you opened during step 3. 

Also, make sure that your lockshield and thermostatic valves are open, so that water can flow into the radiator you were working on.

You’ll need to re-pressurise your system to make sure everything is working properly. Finally, bleed your radiator one more time to let out any air that became trapped inside as it refilled. Use an old rag or towel to clean up any messes, as the water might be discoloured.

If all has gone well, your new valve should be working perfectly!

Can you change a radiator valve without draining the system?

Yes, you can change your radiator valves without draining your whole system of water.

It’s quite a difficult task, though. We don’t recommend trying it yourself unless you’ve got a lot of experience with radiator-related jobs. If you’re unsure about anything, it’s always best to call in a professional. 

If you do decide to give it a go, you’ll need to start by following steps 1 and 2 as described above. Once you’re ready, with water and heating switched off and towels on the floor, you can follow these steps. 

1. Use your radiator bleed key to release the stored pressure inside your radiator. Once this is done, close the bleed valve again. 
2. Open the old thermostatic/manual valve. Do this by holding onto the body of the valve with your wrench, and using a spanner to loosen the top nut. Water and air will start to flow out of the radiator. Make sure you have a container on hand to catch the water, which should keep flowing for a few minutes until the radiator is drained. 
3. Once the water has stopped flowing, remove the old valve entirely. 
4. Attach the new TRV, in the same way as described above. 
5. That’s it! Time to repressurise the system, bleed your radiator, and check that everything is in working order.

You’re in safe hands with our boiler cover

All this talk of valves, nuts, and wrenches got you feeling stressed out? With OVO’s boiler and heating cover, you won’t have to worry about taking on these tricky jobs yourself. 

Our Gas-Safe registered engineers are always on hand to keep your central heating system in working order.

For as little as £15 a month, you could get unlimited call-outs. Not to mention, your monthly fee will cover the cost of repairs, including parts¹. 

Find out more

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