Radiator Repairs & Replacement

A TRV that doesn't respond is usually either stuck (common if it hasn't been turned in a long time, particularly after summer) or has a failed internal pin mechanism, and the difference matters because a stuck valve can sometimes be freed rather than replaced, while a failed pin needs a new valve. It's a common and generally straightforward fix either way, and doesn't usually require draining the whole system if only that one radiator is isolated.

If the radiator itself is sound (no corrosion, correctly sized for the room, no other faults) and the leak is genuinely coming from the valve rather than the radiator body, replacing just the valve is the sensible and cheaper option. Replacing the whole radiator only makes sense if it's also undersized, visibly corroding, or old enough that other faults are likely to follow soon after.

A radiator that's undersized for its room will struggle to bring the room up to temperature even when it's fully open and the rest of the system is working correctly — it'll feel hot to the touch but the room itself stays cool, especially in colder weather. This is a genuinely common issue in older UK housing stock where radiators were sized to an older, lower heating standard than current expectations; it's a design question rather than a fault, and the fix is a correctly sized replacement rather than a repair.

In most systems, individual radiators can be isolated using their own valves and replaced without draining the entire system, which keeps disruption and refill time to a minimum. The exception is where the isolation valves themselves are old or seized and won't hold — in that situation the valves usually need attention too, which is worth flagging honestly rather than discovering partway through the job.