Installing a new radiator in a new position requires a little more consideration than just replacing an old one. It can be fitted anywhere along the flow and return of the central heating pipes, but care should be taken not to diminish the boiler output to existing radiators. Generally, flow rates in pipes should allow for no more than three radiators to 15mm / ½ in of flow and return. However, if the radiators are larger than 1 metre long or the piping is over 4 metres then there should be two or less.

If your installation is not a replacement, it will be necessary also to work out the optimum size and position of the new radiator. The output of a radiator is denoted by British Thermal Units and kilowatts. A rough calculation of what you need will involve:

Cubic feet room volume x 5 = BTU temperature required.

Radiator ValvesFor example; a room measuring 4m x 3m that has two un-insulated cavity walls will require a radiator of about 3kw; this will achieve a 21°C temperature inside when it is -1°C outside. Radiators with larger outputs have an individual thermostat control. These are often found with vented central heating systems. To feel the most effect from your radiator, it is best installed in the coldest area of the room, usually on an outside wall and often under a window.

Before undertaking major work on any part of your heating, ensure that you drain the central heating system first. (See Draining the Central Heating System page).


It is a good idea to fit the valves on before the radiator is hung so that you can judge where the pipes will come from the floor. If the valve is above a joist you can either move the radiator a little or bend the pipe.Wrap some PTFE tape around the threaded tails of the valves and screw them into the radiator, either with an Allen key or a spanner. One valve has the knob for the radiators on/off control, while the other is a lockshield.

Hanging a radiator:

Fitting a radiatorPut the radiator on the floor in the position you want to hang it. Using a pencil, draw a line on the wall along the top of the radiator. Looking at the back of the radiator, place on the brackets and measure the distance, then transferring this measurement to the wall by drawing vertical marks corresponding to the centre line of the bracket straps. This will give you two crosses on the wall to position the wall brackets.

Line up the brackets with the marks and drill a hole through each slot. Before drilling, always check there are no cables or pipes behind. Screw the brackets onto the wall and hang the radiator, checking if it is level. If it is level, screw through the bracket holes to finish the task. If not, tap the higher bracket to balance it out.


Radiator PipeworkThe pipes can run along the wall or from under the floor. If they are coming from the floor you will need to mark the holes with a right angle, holding it in line with the valve positions. The drill bit will need to be 18mm to give enough clearance. A hole that is too small will make the pipes squeak.

To joint the pipes, one option is to use push fit joints. These need to be cut evenly with a pipe cutter so that they do not damage the rubber seals when the joints are attached. For soldering, ensure that you have a heat resistant mat to protect the surrounding area.

Once the installation is complete on a vented central heating system, allow water back into the feed and expansion tank for the system to fill. All radiators will require bleeding to balance them. For a sealed system or one with a combination boiler, activate the filling loop so that water fills the system and the pressure gauge states 2 bar. Bleed all the radiators until the pressure it at 1 bar, topping up with filling valve as you go.