Are radiator valves universal?

Posted in: Radiators
A pair of chrome valves attached to a heated towel rail

There's a lot to think about when upgrading or installing radiators and central heating systems and radiator valves are a key component of that.

Fortunately, valve sizing in the vast majority of homes in the UK is pretty easy. Valve size refers to the width of the connections and the UK standard are 15mm radiator valves. The standard size of copper pipes in UK homes is also 15mm.

However, there are sometimes exceptions to the 15mm rule and below we offer a guide to all the radiator valves sizes that are available.

UK radiator valve sizes

  • 15mm valves - The UK standard valve size. The biggest range of styles and finishes are available in this size and is probably the size you need.
  • 8mm valves - Used for narrower 'microbore' pipes which were popular in the second half of the 20th Century as a way of reducing water usage and heat loss.
  • 10mm valves - A slighter wider type of microbore pipe. Unless very well-maintained, microbore pipes are more prone to blockages.
  • 22mm valves - Occasionally found in bathrooms where a greater flow of water is needed from the hot water tank.

View Our Radiator Valves By Size

Measure your pipes

A Thermostatic Radiator Valve

You'll probably need a set of 15mm valves for your radiator, but if you're unsure then measure the diameter of your copper pipes to double check.

The connection between your valve and the radiator is standard across all moderns radiators and valves. The size differences listed above refers to the width of your pipes that the valves will slot onto.

Most of the time it's 15mm, but measuring your pipes will confirm. At Trade Radiators, we sell a fantastic range of 15mm, 8mm, 10mm and 22mm valves.

View All Our Radiator Valves


A pair of brass microbore reducers for adapting your 15mm radiator valves to fit 8mm or 10mm microbore copper pipes.

If you find that you have 8mm or 10mm microbore pipes in your home and don't want to go to the trouble of replacing them, or are having trouble finding suitable valves, then you can also buy a 'reducer'.

Reducers are adapters that allow you to connect a standard 15mm radiator valve to an 8mm or 10mm pipe. They're inexpensive and easy for a plumber of heating engineer to install.

We sell a range of reducers that will fit your valves and microbore pipes.

View All Our Reducers & Adapters


• The complete guide to radiator valves

• How to choose the right radiator valves

• Do heated towel rails need thermostatic radiator valves?

26 January 2021