How to fit a central heating radiator

Central heating radiators form part of a central heating system. These systems are powered by hot water produced by a boiler. All central heating radiators have four holes, meaning four valve points, one in each corner:

• one is the hot water feed or inlet which runs to the boiler;

• one is the return outlet which takes the cool water back to the boiler;

• one is for the bleed valve which is used to remove excess air from the heating circuit;

• the final one can be fitted with a blanking plug and is there to allow for different installation layouts.

Please note: it is imperative to choose the right size of central heating radiator to make up for any heat loss in the home. The power output of a radiator depends on the size of the room you want to heat as well as the quality of the home's insulation.

Bleed valve

A central heating system contains water, but air can also infiltrate the top of the installation which will prevent the radiator from working correctly. That's why it's important to bleed the radiator. The top of the radiator features two holes; one of these should be used to fit a bleed valve. The bleed valve looks like a little cap with a screw in the middle which is turned to get rid of excess air. It is necessary to bleed radiators regularly to ensure they can perform efficiently.

Radiator valves

A radiator valve must be installed on the hot water feed and allows you to control the flow of hot water and therefore the heat output of your radiator. Heat output can be adjusted in one of two ways:

• using a manual wheelhead valve;

• using a thermostatic radiator valve (TRV) to adjust the flow of water to match the temperature of the room.

Lockshield valve

A central heating system incorporates a boiler fitted with pump (generally known as a central heating pump or circulating pump) which is used to send hot water to the radiators or underfloor heating system, depending on the installation. This means that the radiators are all placed at different distances to the boiler. However, water will always take the shortest journey meaning that the closest radiators to the pump will have a higher heat output than those located further away which may lack in power. To account for this phenomenon, a lockshield or regulating valve can be fitted to your radiators. This valve features a spindle which can be used to restrict the flow of hot water to the closest radiators to the boiler and to open those located further away. This process is called balancing the central heating system.

Hot water naturally rises while cold water descends. It is therefore best to have the hot water feed at the base of the radiator to ensure the whole radiator warms up and not just the top.

While most models feature bottom inlets and outlets, you will occasionally find a top entry feed.

The lockshield or regulating valve can be fitted on either side of the radiator on the bleed side or the feed side. But bear in mind that, as detailed above, water will always take the shortest route. Imagine that if you have a very tall radiator and the feed and return are on the same side. The parts of the radiator on the opposite side will contain slightly less hot water than the side with the valves. So to ensure that the radiator can perform efficiently, it is best to have the return on the opposite side to the feed. This means that all parts of the radiator should heat up evenly.

Securing the radiator

Central heating radiators can be secured in three different ways: to the wall, to the floor or even to the ceiling and floor.

Wall mounted radiators

Most radiators are made of steel and designed to be secured to the wall via brackets or clipped into place using hooks.

Floor standing radiators

Cast iron radiators are generally very heavy meaning they can usually stand up on the ground. It's also possible to find floor standing aluminium radiators but these models must be secured to the ground and cannot measure over a certain height. They are often used in front of glazed walls or in conservatories where space is limited.

Vertical radiators

Vertical radiators are designed for rooms with significant heat loss and spaces where there is not enough wall space to install several radiators. The fixings of these radiators can vary but many can be secured using brackets on the floor and even some suspended from the ceiling.

Steps

1. Unpack the radiator and check the components

2. Fit the thermostatic, bleed and regulating valves

3. Take measurements and secure the radiator

4. Connect the radiator to the central heating

• Remove the radiator from its packaging taking care not to damage the front-facing side.

• Identify all the different accessories (brackets, plugs, etc.) and take a look through the installation guide.

Central heating radiators come with plastic caps to prevent dust getting into them. These caps should be removed before the radiator is fitted.

Remove the plastic caps and fit the valves

• Remove the plastic caps covering the holes in the radiator.

• Fit the thermostatic valve or wheelhead valve to the radiator on the side you have chosen. Bear in mind that if you are fitting a thermostatic valve, this should generally go on the feed side of the radiator. It is not usually necessary to seal the pipe with PTFE tape or plumber's hemp as most valves come equipped with a rubber seal. However, be prepared to do so if necessary.

• Secure the valve using a radiator valve key or spanner.

Fit the bleed valve and blanking plug

• Fit the bleed valve to the top of the radiator on one side. The bleed valve should also contain its own rubber seal. Tighten the valve using an adjustable spanner until the seal is compressed.

• Check that the screw on the bleed valve is closed using a slotted screwdriver. This will prevent water from leaking out during installation.

• Screw the blanking plug onto the other side of the radiator.

Install the lockshield valve

The lockshield valve usually forms two parts: the tee piece itself and a nut which is used to screw it into place. These valves are generally designed to be secured by tightening a connection on the inside rather than the outside. You therefore need a special lockshield key to fit a lockshield valve.

• Insert the key into the fitting and tighten until the rubber seal inside is compressed.

• Thread the connection into place.

Some radiators come with a template for installation. Otherwise, you will have to measure each side of the radiator.

• Fit the brackets to the radiator.

• Measure the space between the brackets.

• Identify the exact spot where you want your radiator to go and note the position of the pipes. Leave at least 10 to 15cm from the ground.

• Mark these measurements on the wall using a tape measure and spirit level.

• Drill your holes for the brackets and insert the appropriate wall plugs for your surface.

• Screw the brackets into the wall.

• Fit the radiator to the brackets.

• Connect your radiator to the pipework and tighten everything into place using an adjustable spanner.

• You can then fill the radiator.

• Be sure to bleed the radiator at the same time using a bleeder and check the pressure. Once water starts to come out of the bleed valve, your radiator is full.

• Check the pressure once again.

• Ensure that each valve is watertight.

• Adjust the radiator using the TRV or manual valve.

• Check that the radiator is heating up across its entire surface.

Time required

1 to 2 hours

Number of people required

1 or 2 people

Tools and equipment

• Water pump pliers

• Adjustable spanner

• Lockshield key

• Slotted screwdrivers

• Hammer drill

• Fixings and plugs

• Spirit level

• Tape measure

• Pencil

• Plumbing tools

Safety and workwear

• Safety goggles

• Protective gloves

• Work clothes

This list is non-exhaustive; be sure to match your safety and workwear to the task at hand.