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A Guide to Radiator Valves

Updated: Jun 17

A closeup of a Cast Iron radiator painted in a custom colour and a designer radiator valve.

Radiator valves control the operation of each radiator in a home. They are as important to the performance of the heating system as the radiators themselves. As such, it is essential that the correct valves are selected to ensure a comfortable environment and prevent wasted energy. There is also now a wide range of styles to suit any interior design.

Radiator Valves: The Basics

Every radiator needs two valves to operate, one on the inlet pipe and one on the outlet pipe. These two valves are called the wheelhead and lockshield respectively and act like taps, controlling the rate at which the water circulates through each radiator.

The wheelhead valve adjusts the flow of water into the radiator and is used to control the temperature of the radiator. The lockshield valve controls the water flowing out of the radiator and helps ensure an even flow of hot water throughout the system.

When new radiators are fitted, the system must be balanced, with the valves of each radiator set according to its position in the system. This process ensures that all the radiators heat up at the same rate when the heating comes on, improving the efficiency of the system.

The Importance of Choosing the Right Valves

When selecting radiators, either for a new property or as a replacement, radiator valves are sometimes given little or no attention. However, the valves have an essential role to play and choosing incorrect or poor-quality products will affect the performance of the heating system.

Types of Valves

There are several different types of valves to suit the requirements of the home as well as the position of the supply and return pipework. There is also a wide range of different styles to complement the radiator or towel rail and the overall aesthetic of the room.

Corner, angled and straight connections

The connection points on the radiator as well as the configuration of the pipework around the radiator will influence the type of valve that is required.

  • Straight Radiator Valves – for where the pipework projects directly up from the floor and connects to the base of the radiator.

  • Angled Radiator Valves – used where the pipework comes up from the floor but a 90-degree connection to the radiator is needed. Angled valves can also be used where the pipework comes through the wall and the radiator has a connection on the base.

  • Corner Radiator Valves – provide a 90-degree horizontal connection and are used where the connecting pipework comes from the wall to a connection on the side of the radiator.

Thermostatic Radiator Valves (TRVs)

TRVs provide automatic control of the temperature. The TRV monitors the room temperature and automatically opens and closes the valve to reach and maintain the set temperature level. TRVs usually provide between four and six temperature levels. This self-regulation of the temperature helps improve the efficiency of the heating system by reducing wasted energy and overheating.

From June 2022, under the latest updates to Approved Document L of the Building Regulations in England, TRVs must be fitted in new homes or when the boiler is replaced. TRVs must be installed on radiators in every room of the property except the room where the main thermostat is located.

Manual Valves

With these valves, as the name suggests, the flow of water into the radiator is changed manually by adjusting the wheelhead valve. With a manual valve, there is a constant flow of water through your radiator regardless of the room temperature. This means the radiators will only turn off when the system thermostat set point is reached or the programmer switches the heating off.

Under the updated version of Approved Document L, manual valves will still be used in certain situations. For example, they may be more suitable for radiators in the room where the thermostat is located. In this case, the main thermostat will, in effect, perform the same function as the TRV by monitoring the room temperature.

At Radiators Direct we have manual valves in various styles. Our Vattimo valves, available in angled, offer a more traditional look. In contrast, the Penco valves provide a more modern take.

Dual Fuel

Towel rails are commonly installed as part of the central heating system, but this means they will not provide towel warming or drying during the warmer months when the heating is turned off. A solution to this is a ‘dual fuel’ option that features an electric heating element to allow the towel rail to work independently of the heating. There are several dual fuel valve configurations available depending on the pipework.

For example, our Corner TRV valve for dual fuel makes the combination of heat sources simple as it includes both the TRV and a lockshield with an integrated T Piece to accommodate the electric element.


Radiators are available in a wide array of styles and the valves are no different. We have options to suit any interior style from sleek modern designs such as the Rota valves to the traditionally styled Pietro valves. These are available in a variety of finishes such as nickel, chrome, antique and polished brass, antique copper, pewter and white.

For a truly integrated design scheme, the new valves, as well as pipe covers and shrouds, can be colour-coordinated with the radiator itself.

What Are Pipe Centres and How Are They Measured?

The pipe centre measurement is the distance between the inlet and outlet pipes for the radiator. It is found by measuring from the centre of one pipe to the centre of the other. It is essential to accurately measure the pipe centre to ensure the radiator can be fitted easily. However, the dimensions of the radiator valves must also be factored into the calculation to ensure the distance between the pipes can accommodate the radiator and valves with minimal alteration. For example, our Ideal valves require an additional 80mm (40mm on each side) that must be added to the width. Therefore a 1000mm wide radiator plus 80mm gives a pipe centre measurement of 1080mm.

The information provided with each radiator will state the allowance that must be made within the pipe centre calculation. While quality valves will generally be produced to an accurate size, manufacturing tolerances must be considered. Therefore, it is always recommended that pipework is not adjusted until the new radiator or towel rail and its valves are fitted.

A white radiator, the picture displays where to measure the radiator width and pipe centres

How to Adjust Your Valves

Having the radiator valves set correctly is essential to ensure the room is at a comfortable temperature and that energy is not wasted. It is important to remember that a TRV opens and closes based on the ambient temperature of the room, rather than the temperature of the radiator. On a TRV, the number on the wheelhead control will dictate how warm the room must be before the valve closes. The higher the number, the higher the temperature must be before it shuts off. It is also important to remember that a higher number does not mean the radiator will heat up faster. In fact, it leads to the radiator working harder or for longer before the room reaches that temperature.

The best approach to correctly setting the valves is to initially turn all the TRVs in the room to a moderate setting (such as 3) and wait for the heating to raise the temperature of the room. If the room is too warm or not warm enough, the setting on the valve can be lowered or raised accordingly. It may be necessary to wait until later in the day or even the following day to assess if the new setting is suitable. Further adjustments up or down can then be made until the right temperature is achieved.

In some situations, having a TRV set to the maximum may cause wasted energy as the heating system will be working unnecessarily. For example, if the radiator is in a room with less insulation or greater air movement, it may not be possible for the room temperature to reach a level that would close the valve. This means the radiator(s) will be on continually, causing the heating system to work harder, with limited impact on the temperature of the room.

How to Completely Turn Off Your Valves

When removing a radiator, for example when decorating, the valves can be used to isolate the radiator and make the procedure more straightforward. Below is a simplified explanation of the process:

  1. Switch the heating system off at the boiler or heating controller.

  2. Turn the wheelhead valve to the 0 or off position. On a TRV it will be necessary to remove the head of the valve and manually close it using a decorator's cap. This is because the freeze protection feature means the valve is designed to not fully close when set to 0.

  3. Remove the cap from the lockshield valve and use grips or adjustable spanners to turn the spindle clockwise until the valve is closed. Providing the valves are fully closed, they will contain the water in the rest of the system, allowing the radiator to be removed without draining the whole system.

  4. Drain the radiator. This can be done by slightly loosening the nut that connects the valve to the radiator and allowing the water to drain out into a suitable container. Start with one valve and then move on to the other.

  5. Loosen the nuts on each valve fully until the radiator can be disconnected from the valve. The radiator can then be removed. It is always advisable to tip the radiator up over a container before it is moved to allow any remaining water to drain out.

Changing a Manual Valve for a Thermostatic Radiator Valve

It is relatively straightforward for a professional to swap a manual valve for a TRV and it is recommended that all radiators in the house are upgraded at the same time. This should be completed by a professional as it is important that the inhibitor in the system is properly checked and topped up if necessary. The system will also need to be rebalanced to ensure optimum performance.

Radiator valves are an important, but sometimes overlooked, part of the heating system. As the component that controls the performance of the radiator, it is important to select quality valves from a reputable manufacturer. At Radiators Direct, we have a wide range of valves to suit any requirement, with design options that will complement the radiator and the room as a whole.

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British Thermal Units (BTU) is a measure of the output of heat needed to raise the temperature of a room. Determining the correct BTU will help you get the right radiator for your home.

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