Whats the difference between On/Off and TRV valves

Whats the difference between On/Off and TRV Valves? This is a common question that we often get asked. The main difference between On/off and Thermostatic valves (TRVs) lies in their functionality and control over heating systems. Here’s an explanation of each type:

On/Off Valves

  1. On/Off valves, also referred to as manual valves or standard radiator valves, are the basic type of valves used in heating systems. They have two positions: fully open and fully closed. When fully open, the valve allows the full flow of hot water or air to pass through the radiator, providing maximum heat output. When fully closed, the valve stops the flow of hot water or air, resulting in no heat output from the radiator.

On/Off valves require manual adjustment to regulate the temperature in the room. Users must manually open or close the valve to control the heat output. This means that once the valve is set to a specific position, it remains in that position until manually adjusted again. As a result, maintaining a stable and consistent room temperature may require frequent adjustments throughout the day.

Thermostatic Radiator Valves (TRVs)

  1. Thermostatic Radiator Valves (TRVs): Thermostatic radiator valves (TRVs) are a more advanced type of valve that incorporates a built-in thermostat. TRVs allow for automatic control and regulation of the room temperature. They consist of a valve body and a thermostatic head, which contains the temperature-sensing element.

TRVs have multiple settings that allow users to set their desired temperature level. The thermostatic head measures the ambient temperature of the room and adjusts the flow of hot water or air to the radiator accordingly. When the room temperature approaches the desired level, the thermostatic head modulates the flow of heat, reducing it to maintain a stable temperature. If the temperature falls below the set level, the TRV opens up to allow more heat flow, raising the temperature again.


TRVs provide better temperature control and comfort compared to on/off valves. They automatically regulate heat output based on the room’s temperature, allowing for a more consistent and stable environment. Additionally, TRVs can help save energy by reducing heat output when the desired temperature is reached, avoiding overheating and unnecessary energy consumption.

It’s important to note that TRVs are typically more expensive than on/off valves due to their added functionality. However, the increased control and energy-saving potential they offer make them a popular choice for both residential and commercial heating systems, as they provide improved comfort and energy efficiency.

Here at Heat & Things, we sell both TRVs and On/Off valves. Below is a small selection of our large range – you can find a link to the full collection here. If you have any questions feel free to reach out to us by email (warehouse@manissa.co.uk) or give us a call on 01325 321 236.