Last November my living room radiator stopped working. Not gradually — one day it was fine, the next it was cold. I bled it first, which is the standard first response to a radiator that isn't heating. No air came out, which meant it wasn't an airlock. I checked the lockshield valve at the other end. That was open. The problem was the TRV.
I called a plumber. He came, looked at it, and quoted me for a full valve replacement — draining the system, removing the old valve body, fitting a new one, refilling and balancing. A significant job, a significant cost, and a wait of two weeks for an appointment. I thanked him and said I'd think about it.
What I actually did was spend an evening researching TRV problems. I learned that a seized TRV head — stuck closed, preventing hot water from entering the radiator — is one of the most common radiator faults, and that in most cases the fix is replacing the head rather than the valve body. I identified my valve as a Myson TRV 2-way with the Contract head — the one with the black bottom section and white triangle markings. I ordered the Myson Standard TRV Replacement Head. It arrived the next day. I fitted it in ten minutes. The radiator has worked perfectly since.
Understanding the Problem
A TRV head contains a temperature-sensitive element — wax or liquid — that expands and contracts with room temperature, pushing a pin in the valve body to open or close the flow of hot water. When the head seizes, it can no longer move the pin. If it seizes with the pin pushed in (valve closed), the radiator gets no hot water and stays cold. If it seizes with the pin released (valve open), the radiator runs constantly.
In my case, the head had seized with the valve closed. The radiator was getting no hot water. The valve body itself was fine — the pin moved freely when I removed the old head and pressed it manually. The problem was entirely in the head, which meant replacing the head was the complete fix.
Identifying the Right Part
This is the step that matters most, and the one that most people skip: correctly identifying which replacement head you need before ordering. The Myson Standard TRV Replacement Head is specifically the replacement for the Myson Contract head — identifiable by its black bottom section and white triangle markings on the dial. If your Myson TRV head has these features, this is the correct replacement.
The distinction matters because Myson makes more than one TRV head design, and fitting the wrong head to a valve body can result in an incorrect fit or improper function. The Contract head is one of the most common Myson TRV designs in UK homes — if your heating system was installed or serviced in the last twenty years and uses Myson valves, there's a reasonable chance this is what you have.
The replacement includes locking pins, which are the small components that secure the head to the valve body. Having these included means you don't need to source them separately or reuse the old ones, which may have worn.
The Installation
I fitted it on a Saturday morning. The process for a seized-closed head is slightly different from a seized-open one: because the pin is already pushed in (valve closed), you don't need to set the head to the open position before removing the old one. Remove the old head by unscrewing the securing ring, lift it off, check the pin moves freely in the valve body (it did), fit the new head, secure with the locking pins, set the dial to the desired temperature.
Ten minutes. The radiator was warm within twenty minutes of the boiler coming on. By the time I'd had a cup of tea and come back to check, the living room was heating normally for the first time in three weeks.
What the Plumber Would Have Done
I want to be fair to the plumber who quoted me. He wasn't wrong that the valve could be replaced — that's a legitimate solution to a TRV problem. What he didn't do was diagnose whether the head or the body was the issue, which would have changed the recommendation. A full valve replacement when only the head needs replacing is the more expensive solution to a problem that has a cheaper one.
This isn't a criticism of plumbers generally — most TRV problems do require professional attention, particularly if the valve body is corroded or the pipework needs work. But a seized head on an otherwise functional valve body is a homeowner fix, and knowing that before calling a professional can save a significant amount of money.
One Full Heating Season On
The replacement head has been on the radiator through one complete heating season. The living room radiator works exactly as it should: it heats when the room is below the set temperature and stops when it reaches it. The locking pins have remained secure. The dial moves smoothly. The black bottom section and white triangle markings look identical to the original head that came off.
I've since replaced the TRV head on a second radiator in the house — the hallway one, which had been slightly erratic for a year. Same process, same result. Both radiators now work correctly, and the house heats more evenly than it has in years.
The Difference It Made
The living room is warm again. That's the practical difference. The less practical difference is that I now understand my heating system well enough to diagnose and fix a common fault myself, which has changed how I approach home maintenance generally. The TRV head was the first thing I fixed by understanding the problem rather than calling someone to fix it for me. It won't be the last.
Who I'd Recommend This To
Anyone with a Myson TRV 2-way valve whose head has the black bottom section and white triangle markings — that's the Contract head, and this is its direct replacement. Anyone whose radiator has stopped heating and who has ruled out airlock and lockshield valve issues. Anyone who has been quoted for a full valve replacement and wants to check whether the head alone is the problem first. And anyone who wants to understand their heating system well enough to fix common faults without professional help.
The key diagnostic step: remove the old head and press the pin in the valve body manually. If the pin moves freely, the valve body is fine and the head is the problem. If the pin is stuck, the valve body may need professional attention. In most cases, the pin moves freely and the head replacement is the complete fix.
You can find the Myson Standard TRV Replacement Head in our store. It also sits within our Heating Radiator Accessories, Household Appliance Accessories, and Home & Garden collections if you'd like to explore more.
Diagnose it properly. Order the right part. Fix it yourself.
— Paul Denton, Nottingham
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