How To Fit A Radiator


Adding a new radiator into an existing system is best left to a professional, but it's possible to update or replace a rusty unit with the same size new radiator using some basic plumbing know-how.

By George Clarke

Adjustable spanners
PTFE tape
Radiator key
Shallow bowl or pan
Old towels


A 600x600mm double radiator costs from £45


Three to four hours for novices


Some plumbing experience needed

Turn Off The Radiator

Step One: Turn Off The Radiator

Turn off the heating and water, and allow to cool. Turn off the radiator by turning the plastic handle clockwise. At the other end of the radiator is a lockshield valve. Take off the protective plastic cap and use an adjustable spanner to close this valve by turning it clockwise. Make a note of the number of turns needed as the valve should be opened by the same amount of turns when the radiator is replaced. This will keep the system 'balanced' - distributing the heat evenly through the house.

Bleed The Radiator

Step Two: Bleed The Radiator

Bleed the radiator of air by using a key to open the bleed valve in one of the top corners of the radiator.

Remove The Old Radiator

Step Three: Remove The Old Radiator

Remove the old radiator, leaving the two valves attached to the pipes. Grip the valve assembly with one wrench so that it cannot be pulled loose from the pipe feeding it. If you open the bleed valve at the top of the radiator, air will enter and allow the water to flow more quickly out of the radiator. Undo the nut completely.

Drain The Old Radiator

Step Four: Drain The Old Radiator

Now, carefully undo the nut holding the radiator to the valve at the other end in the same way. Close the bleed valve. Lift the radiator up from its brackets and hold it at an angle over the bucket to finish draining. Radiators can be fairly heavy, so get some help.

Attach The New Radiator

Step Five: Attach The New Radiator

Wrap a short length of PTFE tape around the thread of the new radiator in a clockwise direction before fitting. Lift the radiator up onto the wall brackets and manoeuvre the valves at both ends so that they sit squarely onto the radiator connections. Hand-tighten the nut onto each valve, taking care not to cross thread them.

Tighten The Valves

Step Six: Tighten The Valves

Holding the valve assembly with a pipe wrench so that it can't be pulled off the pipe, use a second wrench to do up the connecting nut. Remember, you can tighten a joint if it leaks, but if it has been over-tightened, you will need to dismantle it and start again.

Open The Flow Valve

Step Seven: Open The Flow Valve

Having tightened both connections, open the bleed valve at the top of the radiator. Now open only the flow valve at the bottom of the radiator. This will be the valve used for turning the radiator on and off. This will allow the water to flow in, and air to be pushed out at the top. When water starts to leak from the bleed valve, close it.

Open The Return Valve

Step Eight: Open The Return Valve

Now open the return valve at the bottom of the radiator by the same number of turns used to close it originally, allowing water to circulate through the system. Check both connections for leaks, turn on your heating and check again for leaks.

  • Bleed all the radiators in your system to get rid of any air pockets and make the system run efficiently.
  • Don't forget to add reflective radiator foil if it is fitted on an external wall to make it more efficient.
  • If you don't have a thermostatic valve fitted, fit one to the new radiator.

Illustrations: Ed Roberts


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