Thermostatic radiator valves are the single most searched product category in the UK heating market — and for good reason. A set of TRVs fitted across a home’s radiators can reduce heating bills by 15–20% by allowing individual room temperature control, preventing rooms from overheating while others remain cold.
Better still, fitting TRVs is entirely legal for homeowners to do themselves. No Gas Safe registration required. With the right valve, some basic tools, and a working knowledge of your drain-down procedure, a full TRV replacement job is a practical DIY afternoon.
Thermostatic Radiator Valves (TRVs)
TRVs replace the standard manual valve on each radiator. A wax or liquid sensor in the valve head expands as room temperature rises, gradually closing the valve and reducing flow to that radiator. When the room cools, the valve opens again. The result is automatic, self-regulating temperature control per room — without a complex control system.
TRV Heads vs Full TRV Bodies
TRV head only: If the existing valve body is undamaged and of standard ISO-compatible stem size, a replacement head is all you need. Heads are far cheaper than full valve assemblies and fit most modern valve bodies without draining the system.
Full TRV assembly (body + head): Required when replacing old-style valves with non-standard stems, Danfoss-style valves needing a Danfoss head, or when the valve body itself is corroded, seized, or leaking.
Angled vs straight: Angled TRVs (the body turns 90°) are used where the pipe enters from the floor or wall below the radiator. Straight TRVs are used where the pipe enters horizontally.
TRV Brands We Stock
- Drayton: Widely used across UK new-build and replacement markets
- Honeywell Home: T series TRVs known for reliability and precise temperature calibration
- Danfoss: Danish-engineered TRVs preferred by engineers for precision
- Myson: Popular for chrome finish options on designer radiators
- Oventrop: Premium TRV bodies with fine adjustment, popular in high-end properties
Manual TRV Operation
In rooms where thermostat-based control is preferred (e.g., the room containing the room thermostat), the TRV should be set to fully open or replaced with a manual valve to avoid conflicting control signals.
Lockshield Valves
The lockshield valve is the return-side valve on each radiator — it has a plastic cap covering an adjustment slot and is used by engineers to balance the heating system. Balancing adjusts each lockshield so that all radiators heat up at roughly the same rate.
Lockshield valves rarely fail but occasionally develop internal seat corrosion or stem deterioration that causes weeping. We stock direct replacement lockshield valves for all standard radiator connections.
Important: When replacing a lockshield valve, note how many turns the existing valve is open before draining down. Return it to the same position after fitting the replacement to preserve your system’s balance.
Manual Radiator Valves
Standard manual valves without TRV function — simply open or shut by hand to control flow to a radiator. We stock manual valves in angled and straight configurations, 15mm and 22mm connections, in chrome and white finish.
Radiator Accessories
Radiator Keys
The most basic radiator accessory — a small square-section key used to open the air bleed valve (bleed screw) at the end of each radiator to release trapped air. Bleeding radiators is the first response to a cold-at-the-top, warm-at-the-bottom radiator symptom.
We stock individual radiator keys and trade packs.
Blanking Plugs
Radiators have four threaded connections — two for valves and two that are blanked off. Blanking plugs seal the unused connections. Available in 1/2" BSP (most common), 3/4" BSP, and 1" BSP. Brass finish standard.
Air Vent / Bleed Valves
The automatic air vent or manual bleed valve fitted to each radiator allows air pockets to escape from the system. Automatic air vents open when air is present and close when water fills the valve.
Radiator Thermostatic Valve Heads
Replacement TRV heads are compatible with most standard ISO-dimensioned valve bodies. Snap-fit installation without draining. We stock Drayton, Honeywell, and Danfoss heads.
System Balancing After Valve Replacement
Whenever you change a valve — TRV or lockshield — it’s worth checking your system balance. An unbalanced system produces hot radiators near the boiler and cold ones at the far end of the circuit.
If you’re not familiar with balancing, our helpline can talk you through the process: 0330 124 5678.
DIY-Safe Work vs Gas Safe Required
DIY-legal: Replacing TRV heads on compatible valve bodies (no drain-down), bleeding radiators, adding magnetic system filter, replacing blanking plugs.
Requires drain-down (competent DIY): Replacing full TRV assemblies, replacing lockshield valves, replacing radiators.
Requires Gas Safe engineer: Any work on the boiler itself, adding new circuits to the heating system, connecting to gas pipework.