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A Quick Guide Installing Radiator Valves

A Quick Guide Installing Radiator Valves

Suparna Chakraborty |

Tools You Will Need:

  • Towel and a catch bowl/container

  • Hose and a Jubilee clip

  • Hex key (hexagonal radiator spanner)

  • Plumber’s wrench & adjustable spanner

  • PTFE tape (thread seal tape)

Step 1: Switch Off the Heating System and Shut Off Water

Safety first. Before you can change the radiator valve, you must isolate the water supply. If water continues to enter the boiler while you are draining the system, it could overheat and burn out the pumps.

  • Turn everything off electrically at the boiler.

  • Turn down all room thermostats.

  • Ensure your programmers/timers are not calling for heat.

🖼️ [Image: Close-up of a person's hand switching off the main power dial on a modern white combi-boiler control panel.]

Step 2: Locate the Drain Off and Empty the System

Find the drain-off valve, which is usually located at the lowest point of your house's heating pipework.

  • Attach a hose to the drain cock and secure it firmly with a jubilee clip. Run the other end of the hose outside to a drain or soil area.

  • Open the drain cock. To speed up the draining, open the bleed valve at the top of your radiator—you will hear air entering as the water empties.

  • Place a towel and a bowl under the radiator valve you are going to replace to catch any remaining drips. Wait about 10 minutes for the system to drain completely.

🖼️ [Image: A yellow garden hose securely attached to a brass drain-off valve on a copper pipe near the floorboards, secured with a metal jubilee clip.]

Step 3: Remove the Old Radiator Valve

With the water drained, you can detach the old valve.

  • Use a spanner to undo the top nut connecting the valve to the radiator, and then undo the bottom nut connecting the valve to the water pipe. Use a plumber's wrench to grip the valve body so it doesn't twist and damage the pipes.

  • Remove the valve. Have your towel ready, as the residual water trapped inside can be dirty.

  • Using a hex key or plumber's wrench, unscrew and remove the old chrome "tail" (the metal piece that screws directly into the radiator itself).

🖼️ [Image: A person using an adjustable spanner and a plumber's wrench simultaneously to loosen the nuts on an old, tarnished chrome radiator valve, with a towel underneath.]

Step 4: Fit the New Radiator Valve

Now it’s time to install your new manual or TRV valve.

  • Wrap the thread of your new chrome radiator tail with PTFE tape (wrap it clockwise so it doesn't unravel when screwed in). Screw the tail into the radiator.

  • Slide the new nut, followed by the new olive (the small metal ring), onto the radiator tail.

  • Do the same for the water pipe: slide the nut on, then the olive.

  • Align your new radiator valve body between the water pipe and the radiator tail. Gently tighten the top nut and the bottom nut. Be careful not to overtighten. Tip: Wrap a cloth around the nuts before using your wrench to protect the shiny new finish.

🖼️ [Image: A shiny new thermostatic radiator valve (TRV) being fitted onto a copper pipe, with a person's hands hand-tightening the connecting nuts.]

Step 5: Turn the Mains Water Back On

Before refilling the system, make sure you close the bleed valve at the top of the radiator and ensure the drain-off valve you opened in Step 2 is fully closed and the hose is removed.

  • If you closed the lockshield valve (the valve on the opposite side of the radiator), remember how many turns it took to close it, and open it by exactly the same amount.

  • Turn your mains water back on and allow the system to refill. Keep a very close eye on the new valve joints to ensure there are no leaks.

🖼️ [Image: A person's hand turning the blue plastic handle of a water mains stopcock valve back to the 'open' position.]

Step 6: Bleed the Radiator and Test

As water fills the radiator, air will become trapped at the top, preventing it from filling completely.

  • Use a radiator key to slowly open the bleed valve at the top of the radiator. You will hear a hissing sound as the air escapes. As soon as a tiny drop of water appears, close the valve tightly.

  • Reconnect the power to your boiler and turn the heating system back on.

  • Let it run for an hour or two, then check your new valve one last time to ensure it is heating up properly and the joints remain completely bone dry.

🖼️ [Image: A close-up of a radiator bleed key inserted into the top valve of a white radiator, with a small tissue held underneath to catch a single drop of water.]