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learn about radiator valves

This guide draws on over 18 years of industry experience to explain everything you need to know about heat output, from basic principles to practical details.

Choosing the right radiator vaves can be daunting - especially imagining how the finished valve will look once finished.

Learn about valve orientation angled, straight and 3 axis valves, and useful setup demonstration images of different valves on different radiators.

Manual Valves and Thermostatic Valves
  • Thermostatic Valves (also known as TRVs) allow you to control the temperature of a single radiator or towel rail within your central heating system. The normal thermostat on your central heating system controls all radiators, therefore not giving such precision control.
  • Manual valves are equal in size.
  • Thermostatic valves are made up of a larger valve (TRV) and a smaller lockshield, so will look imbalanced compared with manual valves. However if you have the right valves they won'y look intrusive.
image showing the difference between a manual set of radiator valves and a thermostatic set of radiator valves
The 3 Orientations of Valves
  • There are 3 orientations (or shapes) of valve: Angled, Straight or 3 Axis Corner
  • Each allows the pipes to be connected to the radiator or towel rail in a different way.
Understanding Orientation of valves - angled straight and 3 axis - demonstration images with arrows to show the parts of the valve which refer to these terms
Which orientation of valve suits which radiator?
  • There are many different installation options for a radiator depending where your central heating pipes are. We have created these simple drawings so you can find your radiator type depending whether it has side or underside tappings (valve entries) and then decide which type of valves you'll prefer for your chosen set-up.
Radiator Valve Setup Images - How Angled, Straight or 3 Axis Corner Valves connect to a radiator - unique sets of images showing all types of valves fit to radiators of all kinds
The 2 primary positions for a valve on a radiator
  • 1. Sides
  • When fitted to the side of a radiator it must be noted that you are
    adding to the overall width of the product, so customers with limited
    horizontal space should opt for radiators that can have underside entry valves
    instead.
  • 2. Undersides
  • Underside entry valves are by far the neatest overall look a the valves are underneath and within the radiator. Terma has really pioneered its radiators to allow for underside entry and its one the
    points that sets us apart from our competitors.
image showing radiator valves connected to the sides of a radiator compared with valves connected to the underside of a radiator
Benefits of underside valve entry - Pipework can be neater
  • We always suggest underside for the valves as overall the look is much neater as the valves won’t look like ears on the sides of the radiator
  • We advise you talk with your plumber and ask what
    they expect your final installation to look like.
  • There is no need for pipework to be on show like seen here on the left.
  • These valves could have been positioned underneath like on the right, with no visible pipework on show.
  • This would have needed a different set of valves - 3 axis and not angled - and often it is the wrong valve choice that forces this kind of somewhat unsightly installation.
Calculating pipe centre measurements on a radiator for the valves
  • The "Pipe Centres" is a term referring to the distance required between the flow and return pipe pipes that will enter the radiator or towel rail.
  • We have created this image below to help you visualise how the pipe centres are calculated for different locations of valves.
  • You need to add or subtract approximately 40mm each for your valves - but if you can ensure you have the valves with you before putting in pipework to be on the safe side and accurately measure it.
image showing how you calculate pipe centre measurements of your radiator dependant on the location of the valves and what you need to take into account for the measurements
Pipe Masking Sets
  • often homeowners have installed fantastic designer radiators and great valves but the pipework installed by the plumber completely lets down the loo - as it had different colour non matching pipework (i.e. chrome) or even white plastic pipework
  • these pipes are 18mm diameter and sleeve over standard 8, 10 or 15mm copper or plastic pipework
  • remember that once your radiator is installed its very timely and costly to go back and fix pipework you do not like the look of and it can be very irritating - so ensure you get the right additional components to finish the look
  • this collection is all our sleeving sets which are in the same colours to match our standard cylindrical valves or traditional valves - we also do complete sets of valves and pipes
image showing how pipe sleeving kits are installed on radiator pipework - shows a period style column radiator with neatly finished pipework and how it has been put together
Hiding copper radiator pipework from show
  • Here you can see how you would hide copper pipework from being on show.
  • You can either sleeve the copper pipework as this is usually 515mm diameter and the sleeving kits are 18mm diameter (this is seen in the image above).
  • Additionally you could buy some 15mm chrome pipe ands solder these on as shown below.
before and after image showing chrome extension pipes being fitted to copper pipework by a plumber - you see the floor before it goes down and how it is connected and the finished installation with the floor tiles down
50mm Connections
  • Typically found on undersides… This is where the distance between the tappings (valve entry points) is set at 50mm.
  • This is very popular in Europe as it allows pipes to be installed in the knowledge the required distance between the pipes will be 50mm.
  • In the UK valves and pipework have been located on the sides meaning the distance between the pipes will vary in line with the width of the radiator - so you can see how these 50mm connections unify and standardise this.
  • When you have set 50mm connections you can also use a different type valve whereby just one valve - known as H Block, mono valve or 50mm connection valves.
image showing a radiator and a towel rail side by side with 50mm pipe and valve connections
Bridging gaps in existing radiator pipework when installing a new radiator which is wider
  • If you have an existing radiator fitted and you replace this with a wider model you may find that you need to bridge the gap in the pipework (if you don't want to re route it all if ti already comes out of the wall at a set point).
  • We offer a range of different size pipe extension pieces for taking adding width to pipe centres where an existing
    radiators pipe centres are wider than the new replacement.
  • Also we offer a telescopic pipe extension piece which can be opened to the desired length as needed.
demo image of how to bridge a gap in radiator pipework which is too wide for the replacement radiator being fitted
What if the Wall to Centre of Inlet and Floor to Centre of Inlet measurements?
  • These are measurements will allow you to install your pipework, ahead of the radiator physically arriving with you. 
  • Although we strongly recommend that you wait until the product arrives before putting any pipework in, as there can always be variances due to products being made by hand.
  • Also your walls and floor might be out slightly.
  • If you wait until the product arrives, you can install the pipes using the product itself as a guide, which is the best option.
image showing how to calculate the wall to centre of inlet and floor to centre of inlet measurements on a radiator for its pipework

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