How to change a radiator valve

Replacing a radiator valve might seem daunting, especially if you're not used to handling home repairs. However, with the right tools and patience, it's a relatively straightforward process.

With the help of Brian Toward, we've broken the repair down into a step-by-step guide that anyone can follow. Whether you're trying to heat a cold bathroom or install a new radiator in your kitchen, these steps will help restore your radiator to working order.

What you’ll need

Before you start your radiator valve installation, here's a list of tools and equipment you'll need:

• Replacement radiator valve
• Adjustable spanner or wrench
• Radiator key
• Bucket or shallow container
• Towels or rags
• PTFE tape (also known as plumber's tape)
• Hex key (hexagonal radiator spanner)

Step-by-step instructions

Before starting the process, make sure your central heating and mains water supply is turned off and the radiators have thoroughly cooled down to avoid any risk of burns.

1. Close the lockshield and manual/thermostatic valves

You'll need to close both the lockshield and manual or thermostatic valve before you begin draining your radiator. This is important for several reasons:

• Prevents flooding – Closing both valves keeps the radiator separate from the rest of the heating system, ensuring no water flows in or out while you work. This prevents flooding and excessive spills when disconnecting the valves and when draining.
• Quicker, easier job – You only need to drain the water within the isolated radiator rather than the entire heating system, making the job quick, clean, and safe.
• Preventing system-wide pressure issues – With the radiator isolated, you avoid system-wide issues such as pressure imbalances or airlocks that could affect the boiler or other radiators, ensuring a smooth replacement process.

Brian explains: " First, close the lockshield valve by turning it clockwise. Be sure to count how many turns it takes to fully close so you can open it back up the same amount later."

" Next, you'll need to close the manual or thermostatic valve, which is on the opposite side of the lockshield. Turn it fully clockwise until you can't turn it further."

2. Bleed the radiator

Locate the bleed valve at the top of the radiator and, using your radiator key, release any trapped air. You’ll know it’s working when you hear a hissing sound as the air escapes. Be prepared with towels or a bucket underneath, as a small amount of water may follow.

3. Drain the radiator

Then, use an adjustable wrench to open the drain-off valve, usually located near the connection point where the pipe enters the radiator. Water will start to flow out, so make sure your bucket is positioned underneath to catch it.

If your radiator doesn't have a drain-off valve, you can loosen the nut on one of the valves slightly to release water.

Brian adds: " Don't rush this part. Let the radiator drain completely, as any leftover water can cause problems during the replacement process."

4. Remove the old valve

Once the radiator is completely drained, it's time to remove the old valve. To do this, use an adjustable spanner or wrench to loosen the two nuts located at the top and bottom of the valve. These are what connect the valve to the radiator and pipework. Gently twist the valve until it comes free, but be careful of any remaining water that could still drip out.

Brian says: " When removing the old valve, taking your time is important. You want to loosen the nuts without damaging the pipework, so steady pressure with the right tool is key here."

Once you've removed the nuts, you'll need to also remove the valve from the tail that connects it to the radiator. This pipe extends from the bottom of the radiator to slot into the valve. " Unscrewing the valve from the tail is easy with a plumber's wrench or hex key," says Brian.

Brian adds: " Sometimes older valves can be a bit stiff or corroded, so using a lubricant like WD-40 can make the process smoother. Just be careful not to apply too much force, as you don't want to damage the radiator."

5. Install your new radiator valve

Next, fit your new  radiator valve. Start by wrapping PTFE tape (plumber's tape) around the valve's threads (the part that connects to the piping system) around four to five times to ensure a watertight seal. Then, slot the new valve into place and tighten the nuts securely using a spanner.

Brian suggests: " You should always use PTFE tape when installing a new radiator valve. This helps create a solid seal that prevents any leaks once the heating system is back up and running."

For a thermostatic radiator valve, make sure you have positioned the valve head correctly. Brian explains: " Position the valve head away from direct sources of heat, like sunlight or a radiator pipe. This helps ensure the valve reads the room temperature accurately and adjusts accordingly."

If you've installed a new radiator, now is also the time to fix your  radiator pipe sleeves to hide the plumbing and create a cohesive design. These sleeves come in a range of colours, including brushed brass, chrome, and matt black.

6. Refill your heating system

Once the new valve is in place, it's time to turn your water mains back on and refill your central heating system. Before you do this, just remember to close the bleed valve you opened in step 2.

You'll also need to open the lockshield and thermostatic or manual valve again to allow water to flow freely back into the radiator.

Once the mains has been switched on, your central heating system should then automatically start to refill with water.

7. Repressurise your heating system

You'll now need to repressurise your heating system to ensure that there's enough water circulating through the pipes and radiators, allowing your boiler to heat your home effectively.

There are a few steps to this:

1. Locate the filling loop – This is a short piece of pipe with a valve on each end, typically found beneath the boiler. It connects the boiler to the main water supply and allows you to manually adjust the system pressure.
2. Open the valves – Turn the valves on both ends of the filling loop anticlockwise to open them. This allows water from the main supply to flow into the heating system, raising the pressure. You should hear a gentle sound of water filling the system, which confirms it's working.
3. Monitor the pressure gauge – Keep an eye on the pressure gauge on your boiler's display as the water flows in. The recommended pressure level for most boilers is between 1 and 1.5 bar.
4. Close the valves – Once the gauge reaches the correct pressure, turn the valves back clockwise to shut them off, one after the other. This prevents over-pressurising, which could damage the system or lead to leaks.

8. Bleed your radiator

The next step is bleeding your radiator again to remove any trapped air.

Brian says: " Bleeding the radiator after installing a new valve is essential. Trapped air can prevent the radiator from heating properly, so you'll want to open the bleed valve and wait until water starts to escape before closing it."