How to Change a Radiator Thermostat Or Thermostatic Valve

There are a few reasons you might want to change your thermostatic radiator valve (TRV), also known as a radiator valve. Attaching a new one can improve your radiator’s performance and efficiency, and you can also upgrade from a manual valve to a TRV to give you more control over your heating. You may also want to change your radiator valve if it gets damaged, or if you want it to look more modern or more in line with your interior design.

Changing this small part of your radiator is a great way to increase its performance without having to replace the entire thing, and it’s a relatively easy job. Keep reading for a step-by-step guide on how to change your thermostatic radiator valve.

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Changing a thermostatic radiator valve can improve heating efficiency, fix leaks or temperature issues, and save you money on your heating bills.
Signs a thermostat valve needs replacing include leaks, no temperature response, cold patches, or a jammed control.
To change a radiator thermostat valve, turn off your heating and water, drain the radiator, remove the old valve, fit the new one, refill the system, and check for leaks.

What is a thermostatic radiator valve?

A thermostatic radiator valve is a clever device that either lets you manually adjust the temperature of your radiators or automatically adjusts to a temperature you’ve previously set. And connected to this is the radiator valve.

There are two different types of radiator valves available; a manual valve that you can adjust to let more or less water into the system, and a smarter thermostatic radiator valve which adjusts the heating automatically. Whichever one you have, you’ll be able to locate it at the bottom of your radiator to the side. It can be either on the right or left.

How do TRVs work?

A thermostatic radiator valve has a sensor which can adjust itself based on your room’s temperature. It allows you to control each room’s temperature individually.

Each TRV will have numbered settings on a dial, usually ranging from 0 to 5, so you can set a barely used room to a lower setting (0 or 1), and a room that you’d like to be warm and cosy to a higher setting (4 or 5).

This is also handy as it means you don’t end up wasting energy on rooms like kitchens which may already be being warmed by an oven.

How do thermostatic radiator valves work?

Inside a TRV you’ll find a valve head and a body. These control the flow of water into your radiator by expanding and contracting to open and close the valve.

You can get two types: A Wax TRV and a Liquid TRV. For both types, as the room heats up, a capsule (either liquid or wax) in the head expands, moving a pin in the valve which closes it. This stops hot water from flowing into the radiator. Then as the room cools down, the capsule contracts, letting hot water back in.

You don’t have to do anything to make this work, it does it all automatically.

How do I know if my radiator thermostat valve needs replacing?

Here are some easy ways to know whether you’ll need to replace your TRV:

You’ve got a leaking thermostatic radiator valve
Twisting the valve doesn’t affect the radiator’s temperature
The radiator has cold patches
The valve is getting jammed

If the radiator is having trouble heating up, bleed it first to see if that fixes the issue. If you’ve never done this before, check out our handy guide on how to bleed a radiator. If it still has cold patches after bleeding, you’ll need to replace the valve.

How do I change a TRV?

So now that you’ve diagnosed that the valve is the problem, how do you replace it? Luckily we’ve put together a simple step-by-step guide to replacing a radiator thermostatic to walk you through the process.

Before you do anything, make sure your heating, boiler, and water are turned off. You’ll also want to allow it to cool for about an hour beforehand. This will help to prevent any accidents or water damage as you’re replacing the valve.

Lay towels down on the floor and place a tub or bucket underneath the valve you’re replacing. There are points in this process where water will drip or flow out of the radiator, so you’ll want to catch this to stop it from pooling on the floor. It’s also a good idea to tape a towel or a piece of cloth onto the wall behind the valve too.

Before you replace the valve in the radiators, you’ll need to drain the system of water. To do this, attach the hose to the release valve, using a jubilee clip to stop it from slipping off. Place the end of the hose outside and open the valve to drain the water from the radiator.

You’ll then need to let in some air at the top of your heating system to replace the water that has been purged. To do this, head to your highest radiator and use a bleed key to open its release valve, and then give the system 15 minutes to drain.

If you’re only replacing the valve in one radiator, you’ll need to isolate all the others by tightening the lockshield valve and turning off the thermostatic radiator valve. This means you won’t be draining the whole system of water just to replace a single valve.

Making sure you’ve got towels and a tub under the valve, loosen the nuts. Use a wrench to hold the valve in place so you don’t bend or damage the pipe. You should now be able to lift the valve away from both pipes.

Align the valve with your pipes and do the previous step in reverse, tightening the nuts to secure the new valve. You’ll then need to add on the thermostatic head, turn it off and place this on top of the valve, turning it until it drops into place. You can tighten it from below with your hands, so there’s no need for a wrench or spanner. Then open up the lockshield valve on the other side of the radiator.

Close the valve used to bleed the air in your highest radiator and shut off the drainage hose before you refill the system. Then you can open up the water supply to refill the radiators and bleed the system. Check the new valve for leaks to make sure you’ve installed it properly. Now your radiators should all work as normal!

How to safely dispose of old radiator thermostatic valves

We recommend you remove the plastic head from the metal body, and then properly recycle the metal element as scrap metal while getting rid of the plastic part according to your council’s recycling guidelines.

It can be a bit daunting taking on a DIY task relating to your central heating system, but fitting a thermostatic radiator valve is much easier than you probably expect. Just make sure to switch off the heating and water before you start work. After that it’s a simple case of unscrewing and removing the old valve and replacing it with a brand new one.

Installing a thermostatic valve is a great way to cut down on heating costs, and now you can take a look at our tips on how to get the most out of your heating system to see how else you can save money.

FAQs

While this is possible, it requires specialised equipment and isn’t advised for DIYers. Draining the system is the safest option.

For a DIYer, it shouldn’t take any longer than a couple of hours to drain the system and replace a radiator valve.

There are several reasons why your thermostatic radiator valve replacement might not be working, including a stuck valve pin, air in the radiator, the thermostat head not attached properly or faulty, system pressure issues, poor placement, or a problem with the system balancing or pump. These could also be the reason your TRV stopped working in the first place. If you’re unable to diagnose this, we recommend seeking professional advice.