Thermostatic radiator valve
In plumbing · also called TRV
A valve on a radiator whose head reacts to the warmth of the surrounding air, shutting down progressively as the room heats up. The numbers on the head are a scale rather than exact degrees. It works best clear of curtains and furniture, and it is normally left off the radiator in the room that has the main room thermostat.
Using Thermostatic radiator valve in a plumbing system
Updated
A distinction worth remembering
Where a radiator is cold points to the fix: air at the top, sludge at the bottom, a valve when it is cold all over, and balancing when only the far rooms lag. Controls then decide when the heat runs and how warm each room gets.
Questions to take further
- Is replacing a boiler notifiable work?
- In England and Wales, yes. An installer registered with a competent person scheme notifies it, or building control is told before work starts. Scotland and Northern Ireland run their own systems, and the gas work goes to a Gas Safe registered engineer.
Sources
- GOV.UK: Approved Document L — Guidance for England on energy efficiency, including heating controls when a boiler is replaced; guidance is not itself the legislation.
- HSE: domestic gas safety FAQs — Gas Safe registration and checking the categories of work on an engineer's ID card.
Where Thermostatic radiator valve fits in the learning path
The Central Heating section covers these topics:
- Wet Central Heating Systems
- Radiators and Heating Controls
- Heating Pressure and Safe Fault Checks
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- Radiators and Heating ControlsCentral Heating
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The valve at one end of a radiator, under a plain cap, that sets how much heating water that radiator receives. It is adjusted when the system is balanced and then left alone. It is not meant as the everyday on and off control for the radiator.
Lockshield valve
Read the Lockshield valve entryCompare related terms
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Lockshield valve
The valve at one end of a radiator, under a plain cap, that sets how much heating water that radiator receives. It is adjusted when the system is balanced and then left alone. It is not meant as the everyday on and off control for the radiator.
Read the Lockshield valve entryRoom thermostat
A control that switches the heating on and off to hold the air temperature set on it, measured where it is fitted. It works best on an inside wall away from radiators, sunlight and draughts. Turning it up higher does not warm a room faster; it only sets a higher target.
Read the Room thermostat entryBalancing
Adjusting the lockshield valves on a heating system so that every radiator gets its share of hot water, rather than those nearest the boiler taking most of it. It is judged by the temperature drop between each radiator's flow and return pipes, compared with the figure the system was designed for.
Read the Balancing entryBefore you start: some plumbing work is regulated or notifiable
Some water fittings work needs notice to, and consent from, the water supplier before it starts. Check the rules where you live.
Gas work is for competent workers covered by a Gas Safe registered business in Great Britain. Northern Ireland has separate gas regulations. Do not work on gas pipes or appliances yourself.
In England, installing an unvented hot-water system over 15 litres is notifiable building work: use a competent installer registered with a competent-person scheme, or tell building control before work starts. Leave this work to a suitably skilled person.
Wales, Scotland and Northern Ireland have their own water and building rules; check which apply before work starts. Electrical connections belong with an electrician.
This guide does not qualify you or make you competent, approved or registered for plumbing, gas or unvented work.
A definition is a start. Using it in a real question is where it sticks.