Designer radiators are the hottest product out there right now, and while you might know what you want it to look like, there’s a little bit of jargon that you might find out there on the web or even speaking to your heating engineer which can leave you feeling like it’s all a bit to complicated.

Not to worry! To help you get a bit savvier with the language the experts throw around, we have taken a lot of time to craft our comprehensive Designer Radiator Showroom Glossary, making awkward conversations where you vacantly nod along a thing of the past!

If you are looking for a term and can’t find it, please feel free to contact us at or call us on 01257 452879, and we will help you directly, and add the new term to our Glossary.

Once you’ve found the information you need, get browsing our brilliant Designer Radiator Showroom range today!


An Airlock is when air becomes trapped within a closed heating system/pipework and is unable to escape on its own; it results in restricted or even no water flow through the pipework. This is commonly caused when the system is filled after draining.

A lightweight material with a distinct appearance when used to manufacture designer radiators. Aluminium is more thermally efficient than its closest counterpart Steel, and so the designs made with it typically hold less water than Steel while producing as much heat output, or more heat output while being cheaper to run. As a soft metal, a drawback for Aluminium is that it is more commonly damaged in transit than other materials.

Valves whereby water enters the bottom of its body, takes a 90° turn and the exits the valve into the radiator. The head of an angled valve set is positioned in line with the initial direction of the water’s entry. Angled valves are most suitable for when pipework approaches from beneath the valve and the radiator has connections on the side (bottom opposite end connections), but will also suit pipework coming out from the wall to fit to any connection positions, though may not be suitable – See our handy valve guide for a full explanation.

Through a process of electrolytic passivation, which increases the thickness of the natural oxide layer on the aluminium, the surface of a radiator can be anodised to better protect it from corrosion. A common finish for Anodised Aluminium is ‘polished aluminium’ which gives the impression that it is reflective like polished chrome, but it is commonly said to have more of a satin appearance.

A plumbing valve installed on the heating system to allow the automatic release of trapped air. When air enters the valve it passes a float in the lower portion of the vent, which allows air to continuously discharge. Once water enters the vent, the float rises with the water and shuts off the valve again. When air enters again the float lowers and allows the air to pass.

A component installed onto the heating system to regulate pressure across each part of the system. It maintains a minimum flow rate through the boiler so that when other water paths are closed the circulation pressure is limited to optimise performance. Certain valves are can be used as Bi-Directional Valves when used in conjunction with an Automatic Bypass Valve

An air vent installed onto a radiator in place of the traditional bleed valve to automatically release any trapped air within the radiator without ever needing to manually adjust it. When air is within the radiator the vent’s inner component dries out and shrinks, opening the vent and allowing air to escape. As soon as the air has been vented the water touches the inner component and it swells up and shuts of the valve, leak free and without effort.


Balance within a heating system refers to each of the radiators being evenly heated to the same temperature as one another. Often once a new radiator has been installed the system’s balance is inadvertently changed because a different amount of water is required to heat the new radiator and so it changes how much hot water flows to other parts of the system. By adjusting the Lockshield valve on each radiator a heating engineer can fine-tune a system to ensure correct heating and pressure throughout.

The bar is a unit of pressure which relates to water pressure in the context of designer radiators, specifically defining the minimum and maximum working pressures for a radiator design, and can also refer to the pressure provided by the boiler on the heating system. 1 bar is roughly equivalent to the atmospheric pressure we experience on Earth at sea level.

A Bi-Directional Valve (specifically a TRV) is designed so that regardless of which direction the water flows through it, it is safe from faults caused by pressure adversely affecting its internal components. A TRV that isn’t bi-directional fitted onto the return side of a radiator can lead to Water Hammer due to its inability to correctly deal with the pressure.

A Blank or Blanking Plug is a threaded component with a closed, flat end used to cap off and seal one of the unused openings/Tappings on a radiator. They range from basic blanks with optional covers, to whole flat, steel heads for a cleaner appearance

A valve screwed into a radiator tapping to allow trapped air to be released. By manually opening the Bleed Valve air will escape and water will fill the radiator again to the top. Once a small amount of water has seeped out (into a tissue a cloth), at that point the valve is closed off again.

Bottom Opposite End connections refer to the positioning of the connection points for the valves. BOE specifically denotes the valves being connected to Tappings on the left and right hand side, positioned towards the bottom of each side.

A mixture added to the central heating system in order to reduce the noise produced by the boiler’s operation, and to improve its heat transfer efficiency.

Brass is used when manufacturing high quality traditional towel radiators. There is a level of prestige associated with Brass rails which is complemented by Brass being a better and more hard-wearing material than the alternative, Steel.

Stainless Steel which has been carefully brush treated to finely scratch the surface of the metal to give it a satin appearance. Different manufacturers have varying techniques to Brush their Stainless Steel, to the extent that two similar designs in Brushed Stainless Steel can still have slight but noticeable finish differences upon close inspection. Brushed Stainless Steel is still bright and reflective, like Chrome or Polished Stainless Steel, but it does not reflect an image, only the light and general colour tones of the subject of reflection.

An acronym for British Standard Pipe, which refers to the standard size of pipework and the connections to said pipework. Often referred to as 1/2″ BSP, or 15mm pipework, all meaning that the pipework and connections to valves and radiators are all of a standard size used across the UK.

Bushes reduce size of the opening of sectional radiators to allow valves to be fitted. The joints which allow a Cast Iron or Steel Multicolumn radiator to be connected together typically feature large threaded openings which need to be reduced in size for normal domestic use. The standard for connection size on a radiator is 1/2 inch BSP to suit normal 15mm pipework. 2 Bushes have threaded openings ready to receive valves, 1 Bush is fitted with a Bleed Vent and 1 is completely closed with no thread at all.

BTU is an acronym for British Thermal Unit. In the context of radiators it refers to a measurement of heat output, allowing you to gauge whether a radiator will be able to heat your space. The technical definition is the amount of thermal energy required to raise the temperature of one pound of water by one degree Fahrenheit. One BTU is equivalent to 1055 joules. This means that the BTUs listed for a given radiator actually define the amount of energy spent to achieve working temperature at a boiler’s given operational temperature (Delta t50 for example). BTUs can be converted to Watts by dividing by 3.412.


A traditional and very heavy material to manufacture radiators from. They have an aged, almost gnarled appearance quality which can’t be matched with Steel or other materials, and so are highly sought after for period properties. Cast Iron radiators are built in Sections which can be joined together to achieve the desired size or heat output required, offering great flexibility. While Cast Iron radiators heat up slowly when compared to Steel or Aluminium, they also retain warmth for longer once the heating has turned off.

A CE Marking indicates that a manufacturer has complied with the requirements that are essential to European health, safety and environmental protection legislation, and can be legally marketed within a given European country.

Central Heating systems feature a boiler to heat water, and a pump which circulates the hot water throughout the pipework within the building to fill and heat the radiators on the circuit, providing warmth to each room, and to provide hot water for taps, baths and showers.

Centres refer to either distance between the Tappings, or alternatively the pipework, from the centre of each Tapping/pipe to the centre of the other. The term Centres most commonly refers to Pipe Centres.

Chrome is the protective layer which is electroplated onto Steel radiators in order to give it a lovely, shiny decorative finish. Similar to painted Steel, Chrome finished radiators typically have 5 year guarantees. Eventually the Chrome will succumb to the atmosphere and begin to deteriorate and peel, but this peeling can be delayed for a significant period (upwards of 25 years) with care to prevent moisture accumulating on the Chrome, especially so with high quality Chrome radiators.

Clearance refers to the room allowed for a radiator so that it is not pushed right up against a wall or the floor. A radiator’s heat output is primarily Convection type heating, so it is crucial to provide ample space for a radiator to be able to draw in cool air at the bottom of the radiator, and push hot air upwards and out at the top. There is no certified requirement for the distance from the height from the floor, but 100mm is advisable as a minimum.

Clearance for Valves refers to the room allowed for the valves to be fitted onto the side or bottom of a radiator. A lot of radiators feature connections on the side, and when this is the case it is crucial to note that your total radiator width once installed will be the width of the radiator plus the width of the valves (minus the Thread length). This can vary from valve to valve, but if you assume that the valves will take up a total of 120mm you will be safe, though for installation purposes allowing for about 150mm or more is ideal as the plumber needs to be able to install the valve itself. For connections on the underneath side of the radiator it is advisable to allow 100mm or more regardless.

Most heating systems are installed as a closed or sealed system, meaning that once filled the water is not exposed to the atmosphere (unlike an Open System) preventing pollutants from entering the system, additionally hot water can be used instantaneously.

A Cold Spot or Patch refers to a part of a radiator which remains cool when the heating is on. Sometimes caused by air being trapped within a radiator at the top, but it is also possible that not enough pressure is reaching the radiator to supply hot water to all parts of the design. This can be quite common with modern vertical radiators, particularly upstairs at the furthest points of the circuit away from the boiler/pump. Turning off all other radiators in the circuit and focusing the system pressure onto the radiator with the Cold Spot can identify whether pressure is an issue. Cold spots can occasionally be caused by a build-up of debris, rust or sludge within a system, and a system cleanse may remedy the issue.

There are typically 2 Collector tubes on a designer radiator where water enters the design and is distributed to all of the other tubes of the radiator. These are the 2 tubes to which all of the rest of the design is welded to, and where the valves and bleed vent typically connect to. In a horizontal designer radiator you might have a series of 20 short vertical tubes all welded to 1 horizontal Collector tube at the top, and 1 horizontal Collector tube at the bottom. In vertical designer radiator you might have a series of 5 long vertical tubes welded to 1 short horizontal Collector tube at the top, and 1 short horizontal Collector tube at the bottom.

Columns refer to the vertical tubes in sequence from front to back of a sectional radiator. The Column depth of a sectional radiator varies normally between 2 to 6 Columns deep. As you move from 2 to 6 columns the radiator becomes deeper, holds more water and generates more heat per Section, as well as becoming significantly heavier.

A Combi Boiler is a space-saving unit which is a combination of a central heating boiler for your heating, and a hot water heater for your taps. Hot water comes out of your taps at mains pressure, making powerful showers possible. They are more efficient and cost effective than a traditional boiler, and there’s no need for a hot water tank.

Thermal Conduction is when heat spreads throughout the metal in a radiator. This is the principle which allows Fins to be added to a radiator in order to increase the radiators ability to heat the surrounding air via Convection, greatly improving the heat output of a radiator without requiring additional water content.

A Convector is a slim component of a radiator, often in the form of a fin, which is designed to be heated up in order to then in turn warm the air in close vicinity to the fin. They are often present in standard, compact style radiators as well as modern aluminium designer radiators. They are designed to have a large surface area in order to warm as much air as possible without dramatically increasing the water content, thus increasing the thermal and cost efficiency of the radiator.

Thermal Convection in heating occurs when molecules close to a hot surface are heated, become excited and begin to spread and diffuse into the surrounding area. This is primary type of heating which occurs in a modern radiator on a central heating system.

A Convection Current is when heated air molecules rise through the channels behind, inside and in front of a radiator and are pushed upwards to the ceiling before dispersing from that point into the available space. Because this hot air is rising, more cool air is drawn in via displacement towards the bottom of the radiator. In turn this new cool is heated and rises, pushing the air above it further outwards into the room, creating a circular current in the process. By this process, radiators are able to spread warmth more quickly to the furthest reaches of a room.

Commonly most household heating systems run at Delta t50, and so heat outputs are commonly provided rated at Delta t50, but occasionally are given rated at Delta t60. When needed, a Correction Factor allows you to adjust from Delta t60 to t50, and vice versa. Starting with Delta t60, multiply the heat output by 0.79 to convert to Delta t50. In reverse, take the t50 heat output and divide by 0.79 to convert to t60.

Valves made around a 3-point corner, whereby water enters the bottom of its body and takes a 90° turn before exiting the valve (sometimes referred to as Flat Fronted Valves). The head of a corner valve set is positioned perpendicular to both the initial entry point and the exit point so that it can be neatly installed in situations where an Angled valve would be obtrusive. Corner valves are most suitable for when pipework is coming out from the wall, and will neatly connect to radiator Tappings on both the side and underneath – See our handy valve guide for a full explanation.


A Decorator Cap can be fitted to valves to close them off, this allows you to remove the radiator and decorate behind it with ease.

Delta T refers to the average temperature at which a radiator’s heat output is given. The most common measure is Delta T50, but a few select manufacturer’s in the industry still provide heat outputs in Delta T60 which states a higher heat output for the same radiator due to the water’s temperature being higher.

Water temperature at the inlet (75°C)/outlet (65°C) of the radiator >> Average temperature = (75°C+65°C)/2 = 70°C >> Delta T50 = 70°C-20°C = 50°C

Water temperature at the inlet (90°C)/outlet (70°C) of the radiator >> Average temperature = (90°C+70°C)/2 = 80°C >> Delta T50 = 80°C-20°C = 60°C

Designer Radiators are the exciting development in the heating industry which adds a new stylish dimension to your household. They typically sacrifice some of their ability to provide heat in order to be designed in more interesting ways, though there are exceptions to this rule in designs with lots of surface area or made from materials such as Aluminium. They operate in exactly the same way as the standard radiators used in most households, but Designer Radiators have the WOW factor a basic radiator does not!

In order to replace a radiator, change a valve set, repair a leak or any other changes and active heating system the water within it must first be drained. First the water feed is turned off, and then a hose is connected to the drain cock to expel the water into a gulley.

Dual fuel refers to when a radiator, normally a towel rail, is installed connected to both the central heating system as well as an internal electric heating element by the use of a T-Piece adapter, to allow the radiator to be used with the electric element independently so that you do not need to use the whole heating system for just one radiator to be turned on.


An Electric Element is a rod or probe inserted into a radiator to heat the water/heating solution inside. When electric current passes through the element it encounters resistance, resulting in the generation of heat.

A European reference system for measuring the heat output of hot water radiators. The EN442 standard defines the method by which a radiator’s heat output must be tested to be certified as EN442 compliant, and is a requirement for any radiators sold within the UK and Europe.


In a standard Convector radiator these are the zig-zag shapes of metal you see when looking down through the grill at the top. For the majority of a radiator’s heat output, hot water within a radiator heats up the surface metal of the design, that metal in turn warms the air around it via convection. The greater the surface area of a radiator the more air that it can heat. By adding Fins which have an efficient flat shape and can heated very easily due to conduction of heat through the metal, the heat output of a radiator is drastically improved. Fins in designer radiators are often added to Aluminium designs in clever and unique ways that aren’t visible upon normal inspection.


The measurement between the floor and the centre of the connection point of the radiator. This measurement is relevant for radiators which are floor mounted, but are being connected to pipework which is going to come out from the wall.

During the installation of a radiator, the Flow and Return simply refers to sides on which the water enters and leaves the radiator. This can be important when using unconventional connection points (top and bottom same end TBSE connections for example) to ensure water enters the radiator at the correct point. It is also crucial when using a TRV set which is not bi-directional and requires the thermostatic Wheelhead to be positioned on the flow side.

A setting on a Thermostatic Radiator Valve which can be used during Winter, or the colder parts of Spring and Autumn, for radiators in rooms you might not use at all, or when you will be away for a period of time. When the valve is operating on the Frost Setting it can detect when the temperature is dropping to freezing or below and gently allows some water to pass through into the radiator in order to prevent it from freezing.


See; Straight Valves

An acronym for Ingress Protection Rating, which states international regulatory guidelines to ensure that electrical equipment and components are safe from moisture and other foreign bodies such as dust, fingers and tools. There are many degrees of sealing effectiveness, and different Zones within a bathroom require greater levels of protection for the electrical goods present depending on how close they are to water sources. The digits (Eg IP54) each correspond to different types of protection, and how effective it is on the item in question;

No special protection
Protection from a large part of the body such as a hand (but no protection from deliberate access); from solid objects greater than 50mm in diameter
Protection against fingers or other object not greater than 80mm in length and 12mm in diameter
Protection from entry by tools, wires etc, with a diameter of 2.5 mm or more
Protection against solid bodies larger than 1mm (eg fine tools/small etc)
Protected against dust that may harm equipment
Totally dust tight

No protection
Protection against condensation
Protection against water droplets deflected up to 15° from vertical
Protected against spray up to 60° from vertical
Protected against water spray from all directions
Protection against low pressure water jets (all directions)  Protection against strong water jets and waves
Protected against temporary immersion
Protected against prolonged effects of immersion under pressure


A Joining Key is used on site to fit together the parts which make up a split sectional radiator. When Cast Iron or Steel Multicolumn radiators reach a predetermined limit, they can no longer be safely built into one piece as it would likely split under its own weight due to the forces acting up it during transit. They are instead delivered in 2 (or more) smaller pieces which require Joining Key to be fitted together.


The term Ladder Rail refers to a basic Towel Radiator made in the shape of a ladder. They feature two vertical Collector tubes, with a series of horizontal ‘rungs’ welded in place from top to bottom. These can be equidistant, but are more often grouped together in fours or fives to increase the heat output and practicality of the radiator.

A Lockshield is one half of a set of valves which is typically fixed and adjusted by the installer to dictate the water flow through the radiator in order to Balance the heating system. The other half of a valve set is the Wheelhead which allows you to turn a radiator on and off.


Valves which are opened and closed by the user manually to determine the flow of water. Manual Valves have some degree of adjustment, but no way to regulate a set temperature like a Thermostatic Radiator Valve, so they require frequent adjustment to keep the room temperature comfortable.

In modern heating the pipework installed for a household central heating system is 15mm in diameter. Microbore pipework refers to any system utilising pipework at 10mm in diameter or less. 10mm and 8mm pipework are both standard Microbore pipe sizes, but are outdated by current valve and radiator connection sizes suited to fit 15mm pipework / half inch BSP connections. While radiators are no longer made to suit 10mm or 8mm pipework, they can still be installed onto a Microbore system using Microbore Reducers, but care needs to be taken to ensure that the lower pressure offered by Microbore pipe is still sufficient to heat the radiator to operate properly.

For Microbore pipework at either 10mm or 8mm, a normal valve can’t connect as standard because the valve’s connection is too wide (appropriate for 15mm pipework). To remedy this, a Microbore Reducer can be fitted to each of the two compression inlets of a pair of valves which is appropriate for the pipework diameter in the property, instantly solving the problem.


A central heating system which is open to the atmosphere and is connected to the mains water supply in order to maintain a level quantity of water within the system. Open Systems tend to exist in older properties, can’t achieve high pressure and allow more corrosive pollutants to access the system requiring more regular system cleansing.


The term Pipe Centres can refer to either the distance between the centre of the left pipe and the centre of the right pipe on the existing pipework (i.e. ‘My pipe centres are…’), or, the distance that the pipework should be apart for a given radiator (i.e. ‘This radiator has a pipe centre of 580mm’). Care should be taken to distinguish this from the term Tapping Centres.

Stainless Steel that has been carefully machine-polished to a near mirror sheen. Polished Stainless Steel has a close resemblance to Chrome, however due to the much higher quality of the material it does not carry the concerns of peeling and corrosion that a Chrome finish Steel radiator would. A distinction should be made that Polished Stainless Steel (as well as Brushed) does not feature layers on the outside, it is solid throughout – what you see on the outside is what you get on the inside.

Pressure refers to the amount of force of the water flowing through the heating system, or to the force exerted by the water sealed within an electric radiator. The measurement unit for pressure is the Bar, and defines the minimum and maximum working pressures for a radiator design

All designer radiators are put under pressure when hot water passes through them in a heating system. The amount of pressure can vary from system to system and depending on the temperature of the water, but the radiators must be pressure tested to define maximum pressure a radiator can safely work at, and the minimum pressure at which it will function properly and heat thoroughly. Most designer radiators are able to work at a maximum operating pressure of 8 or 10 bar.

PTFE Tape is an acronym for Polytetrafluorethyle Tape which is a sealing tape used by heating engineers on the threads of valves/radiator connections to ensure that the seal is water tight and won’t leak once the heating system is filled again.


The term Sections refers to the individual radiator pieces which when joined together build a larger Steel Multi-Column or Cast Iron radiator. Each section can range in height from less than 300mm up to nearly 3000mm in specific cases. They can range in depth determined by the number of Columns from front to back which start at 2 Columns deep and progress to 6 Columns deep. Each section is the same width (i.e. 46mm), and once joined together are fitted with end caps referred to as Bushes or Bushends which reduce the connection size down to 15mm/half inch BSP. By this incremental, sectional nature it is possible to create a radiator size to suit any need.

Two lengths of tastefully finished pipe designed to fit directly over and hide the standard 15mm/half-inch BSP copper pipework. Accompanied by two circular plates designed to press up against the wall or floor to conceal the opening where the pipework comes from. The finishes available all match the finishes available for the accompanying valves.

Similar to a Sleeving Kit, a Shroud is a cover for the pipework, however is more commonly made from plastic, or some kind of wrap-able/snap on material to all them to be retrofitted to existing pipework after a radiator has already been fitted.

Stainless Steel is a steel alloy which is made by combining normal steel with Chromium so that it makes up at least 10.5% of the overall mass. In Designer Radiators this is a fantastic material to use as it is nearly as efficient as normal steel in heat output, and stands up to corrosion both internally and externally much better than Steel, Cast Iron or Aluminium. As a result, Stainless Steel often benefits from long manufacturer guarantee periods of 20-25 years, and occasionally even lifetime guarantees. Stainless Steel comes in two primary finishes: see; Polished Stainless Steel and see; Brushed Stainless Steel

Steel is the most common material for both normal and designer radiators to be manufactured from. It is strong, easy to work with, relatively inexpensive and can be painted in hundreds of finishes, or even plated in chromium for a lovely polished appearance. Steel radiators are typically thermally efficient when painted, though can lose between 15%-30% of the total heat output when Chrome plated as the Chrome acts as an insulator, this just means you would need a slightly larger radiator in Chrome than the size of radiator needed in painted Steel.

A traditional designer radiator design often referred to as an ‘old school radiator’ which is very common, and close variations on this style are provided by most designer radiator brands. A Steel Multi-Column consists of individual Sections (sometimes referred to as elements, not to be confused with Electric Elements) which are joined together and sealed section by section, resulting in the ability to make them on a bespoke basis very quickly.

Valves whereby water enters the bottom of its body and flows directly through before exiting the top of the valve without any change in direction (sometimes referred to as In-Line Valves). The head of a Straight valve set is positioned perpendicular to the initial entry point. Straight valves are most suitable for when pipework is coming up from beneath / up from the floor, and will neatly connect to radiator Tappings on the underneath – See our handy valve guide for a full explanation.


A T-Piece adapter is a small component shaped like an upper case T which is fitted to the Tapping on a radiator allowing both an Electric Element to be inserted and a radiator Valve to the same connection point, thus allowing for Dual Fuel heating. The principle is very similar to that of a double adapter on an electric plug socket.

The exposed pipework which is visible between the floor or wall (depending on where the pipes come from), and the radiator’s valves.

A Tail Extension is a small component inserted into the tapping which features a male thread for entry into the radiator and a female thread to allow a valve to connect into its other end. It is primarily used on radiators with BOE connections (on the side) to widen the natural pipe centres of the radiator to help in situations where pipework cannot be moved – this removes the need to add turns or bends to the pipework, and as a result means you can fit a Sleeving Kit for a much neater appearance.

A variation on a normal thread where the threaded opening becomes narrower the deeper a male thread is screwed in. When a male thread is mated to the Tapered Thread, they compress and tighten to form a seal.

A tapping is the opening on a radiator with a female thread to allow a radiator Valve, Electric Element, Tail Extension or T-Piece to be screwed into. Radiators typically have 4 Tappings, but occasionally have 6.

For BOE connections a Tapping Centres are defined as the distance between the opening of the left tapping and the opening of the right tapping at their widest point. For underneath connections the Tapping Centres are defined as the distance from the centre of the left tapping and the centre of the right tapping. Care should be taken to distinguish this from the term Pipe Centres.

See; Tail Extension. A telescopic or adjustable variant which allows greater flexibility that a Rigid Tail Extension, with a slight aesthetic trade-off.

A Thermostat is a device which allows you to determine a desired heat level and maintain it either automatically, or notifies you to adjust it manually. Most homes have a house thermostat to adjust the overall temperature, and some homes will have floor or even room specific thermostats. Radiators themselves can be fitted with Thermostatic Radiator Valves in order to gain specific control over the temperature of each room.

Thermostatic Radiator Valves (or TRVs) are valves which can be set to reach a desired level of heat within a room and then maintain it. They feature a numbered dial ranging from 1 to 5/Max to set the heat, as well as a Frost Setting to prevent the water from freezing in the winter. The vast majority of TRVs operate using a simple mechanism utilising a pin at the base of the TRV head which closes the valve when pushed down, and a component in the head itself which swells up as it gets hot, pushing on the pin and closing the valve again. Once the temperature has dropped slightly the swelling is reduced and the valve opens allowing it to get hotter again. As you open the valve from setting 1 to 5, the head gently unscrews (it cannot come off!), this moves the swelling component further away from the pin so that it needs to become hotter in order to swell enough to push on the pin close the valve again.

A Thread refers to the spiral design either internal to the connection on the radiator (female), or the external spiral design on the Valve or Electric Element either the female thread on the connection point on the radiator, or the male thread on the Valve, Electric Element, Tail Extension or T-Piece to be inserted into the connection point.

A way of installing the valves so that the Wheelhead (the valve you control) is situated at the top of the radiator, while the Lockshield is positioned at the bottom on the opposite side of the radiator. This is useful in installations for the elderly or those with disabilities as the control is positioned at waist height so the user doesn’t have to bend right over. It is also common in commercial installations where the appearance isn’t quite as important.

A way of installing the valves so that the Wheelhead (the valve you control) is situated at the top of the radiator, while the Lockshield is positioned at the bottom, both on the same side. This is useful in installations for the elderly or those with disabilities as the control is positioned at waist height so the user doesn’t have to bend right over. It is also common in commercial installations where the appearance isn’t quite as important.

A Towel Radiator, or Towel Rail, refers specifically to any radiator which is designed to hold towels and is usually installed in bathrooms, but occasionally is used in Kitchens. The term Towel Radiator or Rail typically describes the standard Ladder Rail design which of course resembles a ladder’s shape, but there or now many gorgeous designer models which go very far beyond the basic or standard shape.


A device used to control the passage of water from the pipework into the radiator, and from the radiator back into the pipework. The main two functional variations in radiator valves are either Manual or Thermostatic operation.
Valve EntryThe connection point on a radiator where the Valve, Electric Element, Tail Extension or T-Piece is connected


The total distance that a radiator will protrude away from the wall once fitted on its brackets. When space is limited within a room, when viewing the radiator from side-on (i.e. in a hallway) or when an object/door will be positioned closely to the radiator the overall depth is very important to consider.

The distance measured from the wall to the centre of the connection point for the valves on the radiator. This measurement is needed when installing pipework coming up from the floor before the radiator is on site as the installer can be precise in the distance away from the way that the pipes are brought up.

Wall Stays are designed to fix a floor-mounted, sectional radiator to the wall. It does not hold any weight, but instead prevents the radiator from shifting or being knocked over and wrenching on the pipework. Wall Stays consist of a threaded rod which is inserted in-between two sections of the radiator, two fixing plates meant to clamp the radiator to hold the stay in place and one more fixing plate to anchor it to the wall. There are basic wall stays which are clamped to the rear of the radiator to keep them hidden, and luxury wall stays which are clamped to the front so they are visible, and finished to match the Valves and Sleeving Kits used.

Water Hammer occurs when due to high pressure a valve suddenly closes causing the flow of water to halt. This results in a large surge of water pressure to build as a wave in the entry to the valve, known as hydraulic shock which results in a shock wave. In the heating system this is identified as a loud banging, which can be compared to noise of a hammer repeatedly hitting the radiator/system. Commonly this is caused by a non-bi-directional TRV being installed on the return side of a radiators flow and can be remedied by placing the TRV side on the flow side, or alternatively using a bi-directional TRV.

In the context of radiators it refers to a measurement of heat output. In heating engineering a Watt refers to the rate of heat transfer, defined as one joule per second (per Watt). Watts can be converted to BTUs by multiplying by 3.412.

A Wheelhead is one half of a set of valves which allows you to turn a radiator on and off. The other half of a valve set is the Lockshield which is typically fixed and adjusted by the installer to dictate the water flow through the radiator in order to Balance the heating system.


Zones refer to the IEE Wiring Regulation which specifies to installers what kinds of electrical components and devices can be installed in specific locations within a wet-room or bathroom. Zones are identified by the distance away from items such as a bath, shower tray or sink. Electrical goods installed within these zones must adhere to the relevant IP Rating for that zone (e.g. IPX5 can be installed within Zone 1).


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Reach us at or call us on 01257 452879 and we will help you directly, and add the new term to our Glossary.

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