Thermostatic Radiator Valves — What They Are and How to Use Them

What Is a TRV?

A Thermostatic Radiator Valve (TRV) is a self-regulating valve fitted to a radiator that controls the flow of hot water based on the room temperature. They allow you to set different temperatures in different rooms, reducing wasted heat and energy.

How Do TRVs Work?

TRVs have a numbered dial (usually 1–5) with a frost setting (snowflake symbol). As the room reaches the set temperature, a wax element inside the valve expands and gradually closes the valve, reducing the flow of hot water to the radiator. When the room cools, the element contracts and the valve opens again.

TRV Number Settings (Approximate)

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Common Mistakes with TRVs

Turning TRVs to maximum — This keeps the valve fully open at all times and offers no temperature regulation or energy saving.

Closing TRVs completely — Fully closed TRVs in winter risk condensation, mould, and pipes freezing. Keep on the frost setting at minimum.

Fitting a TRV in the room with your thermostat — The thermostat and TRV will fight each other. The room with your main thermostat should either have no TRV, or the TRV should be set to maximum.

Not using TRVs at all — Running all radiators at full heat when rooms don't need it wastes significant energy.

Smart TRVs

Modern smart TRVs (like Hive, Tado, or Drayton Wiser) can be controlled via smartphone and set on a schedule — giving you even more control and savings. We can advise on and fit smart TRVs as part of a heating controls upgrade.

For advice on TRVs, heating controls, or any other heating matter, contact Halo Heating on 01483 676108.