How to Change a Radiator Valve

Swapping a radiator valve might sound like a job for the pros, but with the right tools, a steady approach and a little patience, it’s something many confident DIYers can handle.

Whether you’re upgrading to a thermostatic radiator valve (TRV) for better control, replacing a leaking valve, or simply refreshing the look to match a new radiator, this guide walks you through the process clearly and safely.

Why change a radiator valve?

Radiator valves do more than just switch your heating on and off. The right valve can:

• Improve temperature control (especially with a TRV)
• Help reduce energy waste
• Prevent leaks and drips
• Elevate the overall look of your radiator

If your current valve is stiff, leaking, outdated or simply not pulling its weight, it could be time for a fresh start.

Tools you’ll need

Before you begin, gather the following:

• Adjustable wrench
• Grips
• Radiator bleed key
• Jointing compound
• PTFE tape (if changing the insert)
• Hose (a standard garden hose works well)
• Cloth or towel

Step 1: drain your central heating system

Before you can start removing your radiator valves you'll first need to remove all water from your central heating system. Although some people claim you don't need to do this, it's always a good idea as it can prevent any water leakage should something go wrong.

For anyone with a combi boiler, the method of draining the system is relatively easy. If your home has a conventional cylinder tank, it can be a lot more difficult to drain the system and this is where we recommend calling in a professional. 

First up, you'll need to cut off the water supply to your central heating. Once this is done, turn down all your thermostats and turn off the electricity to the boiler. Don't skip this last step as some combi boilers have a habit of switching themselves back on, even after being powered off.

Once you've turned everything off it's time to drain the water from your system. To do this you'll need to find the drain cock. You should use the drain cock which is the closest to and below the radiator you're going to work on.

Next up you'll need to grab a hose (any garden hose is fine) and plug it into the drain cock. Put the other end of the hose outside, somewhere that the water can easily drain away. Once you're happy that the hose is connected and you've double checked the other end is outside, use your spanner to loosen the drain off until water begins to move through the hose outside. 

Next you'll need to open the bleed valves on all the radiators in your home to stop anymore water flowing into your radiators and help more water drain out. Opening these valves can also stop any other radiators in your system retaining water which could be released later on.

Take your radiator bleed key and fit it to the bleed valve. You can then turn the key and open the valve fully.

Your system will usually take around 10-15 minutes to drain completely, so be patient!

Step 2: loosen and remove the old valve

Once you're confident your heating system has been drained completely, you'll need to undo the two nuts connecting the valve to the radiator.

Take a pair of grips to hold onto the body of the valve, then loosen off the nut closest to the radiator with your wrench. Turn the nut slowly anti-clockwise but don't remove it completely.

Now do the same again with the nut at the bottom until you can wiggle the valve to remove it.

For simplicity, many people will leave the existing nuts and olives from their old radiator valves in place and use them with the new valve. For the rest of this guide we'll assume that's what you've decided to do but we've also included a short guide to changing your radiator insert below.

Step 3: clean the pipework

With the valve removed, it's important to use a cloth to clean the area where the new valve will go.

Step 4: apply jointing compound

Jointing compound helps to create a strong seal and keep the valve firmly in place. Add the jointing compound to the two olives on your radiator.

Step 5: install the new valve

With clean pipes and the jointing compound in place, you can now install the new valve. 

When installing the valve, it's important to check the arrows that illustrate which way the water should flow. In many modern valves the arrows will point in both directions, these are universal valves and the water can flow in either direction. For valves with only one arrow, the arrow should point in the direction that water will flow into the radiator.

Position the valve over the pipe then tighten each of the nuts by hand. Now grab your wrench and grips and tighten both nuts up using the same method as when you removed them.

If you're fitting a thermostatic radiator valve (TRV), you can now install the TRV head to the top of the valve.

Step 6: refill and check your heating system

Before you turn your heating system back on, double check that you've tightened both nuts on your new valve. Then you'll need to go round and close all the bleed valves on the radiators that you previously opened. Make sure you've closed the valves on all the radiators because if you leave a valve open on just one radiator, water will come out when the system is turned back on.

Once this is finished, you can close the drain cock and disconnect your hose.

If your heating system is gravity fed, you can now turn on the water supply in the same place you switched it off earlier. Once you've done this the radiators in your home should begin to fill up with water. As this happens, it's a good idea to keep an eye on your new valve and the other radiators in your home in case of any leaks.

The last step is to bleed all of your radiators. This will ensure they're all properly filled and there's no air trapped in the system. When refilling and bleeding your system, we'd recommend adding inhibitor to keep your radiators working at their best.