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How to Fit a Radiator to the Central Heating System


5 Steps explained

Choosing and buying a new radiator might not be such a difficult task in its essence as long as you kept in mind some important ideas like:

  • The radiators should have at least a 2-year guarantee.
  • They should be pressure-tested to 152.3 PSI (10.5 bar) in order to be able to handle a pressure of 116 PSI (8 bar) at a temperature of 95°C.
  • The output of the radiator should comply with the  BSEN442 European standard for radiators.

If you do not resort to a specialist’s help, here are some tips that you should take into account when replacing an old radiator and that can be quite easily implemented. Connecting a radiator to an already existing central heating system is a pretty straightforward DIY job that can be conducted in a matter of hours.

The aim of this article is to provide a tutorial on how to fit in a new radiator yourself without the help of a professional plumber. I will provide some tips on how to choose the location of the radiator, on how to remove the old radiator (if applicable), how to fit the new radiator to the wall, some tips concerning how to cut a pipe, how to connect the new radiator and finally, how to deal with corrosion.

1. Location of the radiator

If you are not replacing an old radiator and you just want to add a new one to the system, you must probably be already aware that radiators are usually placed where the draft enters the house, somewhere near a window or near the entrance door. Now you should be aware that there are problems with both locations; for instance, if you place a radiator near a window, the length of the curtains could have a negative effect on the way heat is distributed inside your home.

Also, the location of the radiator near the entrance door might pose some problems in case you have disabled persons or children in your family. Derived from the curtain problem, you should make sure consequently that you leave enough room for the heat to circulate and for the valves to be installed. The distance between that base of the radiator and the ground should be of approximately 150 mm, at least.

*Note: depending on the type of radiator, you should leave a specific distance between the wall and the radiator as well:
- 40-46 mm for single panel
- 58-65 mm for double panel
- 35-44 mm for single convector radiators
- 60-71 mm for double panel plus
- 71-84mm for double convector.

Another factor that should influence your decision to place the radiator somewhere is the position of the pipe. You should be aware that there are two types of pipes – flow and return. Older system might just have one pipe playing the double role.

In a single pipe system, there is a flow pipe that takes the heated water from the boiler while the return pipe brings the water to the boiler to be heated again. In twin pipe system, you should first try and fix the radiator tails (screw fitting that should come with a lock shield or  thermostatic radiator valves).

Before screwing it to the radiator, you should put some PTFE tape around the thread in order to improve the quality of joints seals. The tails could be quite easily tightened with a radiator spanner.

2. Removing the old radiator (if applicable)

If you are not replacing an old radiator, you can skip this section. If you are replacing a radiator however, there is some advice that you should take into account:

  • Switch off the central heating. If you have conventional heating though, you should stop the cold water from coming to the tank or tie the ball valve so that refilling is not permitted. Another exception is a conventional vented system, in which case you will have to take the water out from the system before physically removing the radiator.
  • Drain off the water from the radiator: (1) You should open the square with a suitable spanner (2) Make sure you have a hose pipe connected to the draincock Type A (see picture below) for a sealed system to deal with leaking water. In a conventional vented system, you could use a hosepipe and clamp it on with a jubilee clip and then try and reach the other point of the hose pipe. (3) Remove all the water in the radiator so that you make sure the water is not going to ruin your house as well.
  • Undo the bleed valve from the radiator so that the water can drain off from the system.
  • When the radiator is empty, you can start undoing one of the valves at the bottom of the radiator; you will probably still notice some water leaking, so you will still have to go and drain some water downstairs. It may be necessary that you should take the water out of the whole system.
  • Remove the fittings and lift it upwards in order to remove it from the brackets.

3. Fitting the radiator to the Wall

Once you have decided on the location of the new radiator, you will probably want to fix it to the wall. In order to do that, you have to follow 5 easy steps:

  • Measuring the distance between two fastening points on the back of the radiator.
  • Drawing a vertical line on the wall employing a bubble level (spirit level).
  • Drawing an additional line to correct the distance apart.
  • Fastening the brackets to the wall.
  • Putting the radiator on to the brackets.

4. Cutting the pipe (better done by plumber)

You need a pipe slice for copper pipes and plastic pipe slicers for plastic.

  • Place a bowl under the pipe since some residual water is likely to come out.
  • In order to place the ‘T’ fitting, you need to cut more from one of the pipes.
  • Make sure you have push-fit fittings and compression fittings at hand.
  • In case you’re working with copper pipes, have a pipe bender and a pipe bending spring at hand.
  • After inserting the ‘T’ fitting, run the pipe from the flow and return pipes to the new radiator (the flow pipe should have the valve on).

5. Connecting the new radiator

Once all the above things were observed, you can finally connect the new radiator:

  • Connect the radiator making sure that the pipe inserts are used.
  • In case you are using compression valves, you should have copper olives since other types of valves may be too hard for plastic pipes.
  • Close the drain off valve.
  • Remove the hosepipe.
  • Close the bleeding valve from the radiator that you might have opened previously.
  • Fill the system again using the cold supply filling loop and if it is a vented system via the water supply system i.e. loft water supply tank.
  • Check new fittings for potential leakages (in case you come across any leakages, tighten the screws or make sure that the pipes are pushed all the way into the fitting).
  • After doing everything, you should bleed the radiator. You can view our previous article, called  How to bleed your radiator in order to get the right information on how to do it.

How to deal with Corrosion

Most people worry about corrosion when installing a new radiator. This is indeed something that you should consider which is inevitable in its essence. What you can do is to prolong the need to replace the radiator. 
Which are the factors that affect corrosion?

  • The type of metal employed in the system
  • The amount of air drawn into the system
  • The type of water that gets into the system
  • The quality of the work for the radiator installation.

What can be done to prevent early corrosion of your radiator? 
Some things you need to do when installing the new radiator:

  • Proper water flushing and filling after the radiator had been installed.
  • Application of some  corrosion inhibitors, in accordance with the manufacturer’s instructions.


In a nut-shell, don’t forget:

  • In terms of  location, make sure that you leave enough room for the heat to circulate and for the valves to be installed.
  • When you  remove the radiator, drain the system out.
  • Fix the radiator to the wall.
  • Cut the pipe (if necessary).
  • Connect the new radiator.
  • Use some  corrosion inhibitors.

Good Luck!

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