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Valve Guide: Thermostatic & Manual Radiator Valves

Updated: Mar 5, 2020

At Foundry Cast Iron we supply a wide range of radiator valves. The purpose of this guide is to help you decide what type of radiator valve you need for your new radiators.

Put simply, radiator valves control the temperature of your radiators. They come in pairs, the valve, and the lock-shield. The valve controls the amount of water entering your radiator (which affects temperature) and the lockshield balances the system.

There are two different types of radiator valves, Manual and Thermostatic (TRV).


Manual valves, like our Arroll Lyminster UK20 Valve, work as a tap. You twist the head of the valve and that controls the water flow into the radiator. This provides a constant heat output, regardless of the surrounding temperature. These are easy to use and usually smaller than TRV's but do have to be operated manually to adjust the heat output.

arroll Manual radiator valve

Thermostatic (TRV)

TRV’s are a bit more advanced than Manual Valves. They work using a temperature sensor (a bit of wax or liquid) that reacts to the surrounding room temperature and stops the flow of water once it reaches the desired temperature. They are more efficient than Manual Valves and automatically turn themselves on and off. These benefits are why our best-selling radiator valve is the Arroll UK28 Thermostatic radiator valve.

Arroll thermostatic valve

Now that you know the difference between Manual and Thermostatic (TRV) radiators valves, it's time to decide which valves fit your pipework. Click here for information about Straight, Angled and Corner radiator valves.



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