Isn’t the first thing most people do when they walk into a room and feel too hot, is turn off the radiator? If so, you are not alone. But what if your radiator does not turn off? It could be stuck on for various reasons. The valve could be stuck open due to a lack of maintenance or if you live in an older building, there may be no thermostat attached to your radiator that allows for room temperature control at all. In this blog post, we are going to have a look at some of the reasons why a radiator will not turn off and what we can do about it.


What is a Radiator?

A radiator is a metal heating appliance that consists of pipes filled with hot water. The pipes are enclosed in a metal box and the room air circulates around it, warming up in the process.

Radiators make use of convection to heat the room as well as conduction (the transfer of heat from one object to another). The core of a radiator is usually made from steel but might also contain copper or brass lining. Steel radiators can get rusty over time which can make them less efficient at heating your home.

Aluminium radiators conduct heat better than steel ones, so they are more popular these days because they are more efficient and durable too!

How Does a Radiator Work?

The process begins when hot water is used to fill the pipes in the radiator. As the thermal mass of this hot water is passed through the radiator, heat is transferred to the air next to it as well as to anything else that is in contact with it.

This gives rise to two forms of heat transfer: conduction and convection.


Convection is heat transfer from a fluid to the surrounding gas (or vice versa) in which the motion of the fluid, called buoyancy, results in circulation. This form of heat transfer will occur when there is movement or flow of a medium such as air or water.

The circulating medium can carry energy away from one area and transport it to another place – this then leads to an exchange in temperature between areas.


Conduction is a form of heat transfer where one particle (or atom) passes on its energy directly to another particle in close proximity. Objects which are touching or are in direct contact will exchange their energy until they reach an equilibrium temperature called thermal equilibrium.

When objects have reached thermal equilibrium, there is no longer any net transfer of heat between them.

Why Your Radiator Won’t Turn Off?

There are several reasons why radiators get stuck on. If your radiator is in a room that is used regularly, it can be turned off using a thermostatic radiator valve (TRV).

These valves allow you to control the heat output from the radiator and will stop heating when the set temperature has been reached. If you do not have a TRV attached to your system, there may be other reasons why your radiator will not turn off including:

The lockshield valve could be stuck open due to wear and tear, or a lack of maintenance, or the system may not have had any sort of thermostat installed at all.

How to Turn Off a Radiator That’s Stuck On

Before looking at how we turn off a radiator that may be stuck on, we need to be sure of what may be causing it so there are a couple of things that you should check first.

Faulty Lockshield Valve

One possible reason your radiator is still hot is that the lockshield is not off. The lockshield is located on the opposite side of the radiator from the TRV valve. To turn it off, locate the lock shield, remove the cap, and use a wrench or pliers to rotate the lock shield and turn it off.

Make sure to keep track of how many turns you give the lock shield so you can turn it back on later.

Faulty TRV (Thermostatic Radiator Valve)

Check that the valve has been turned to the “off” position – you would be surprised how many people panic and overlook the simplest of tasks. A TRV is a valve that controls the temperature of each individual radiator in a heating system.

If a TRV is faulty, it can cause the radiator to remain on, even when the thermostat is turned off.

To diagnose this issue, check the TRV on the radiator in question. If the valve is stuck in the open position or the temperature adjustment is not working properly, it may be faulty and will need to be replaced.

TRV Radiator Valve
TRV Radiator Valve

Faulty Thermostat

A thermostat controls the temperature of the entire heating system by turning the boiler on and off. If the thermostat is faulty, it can cause the radiators to remain on, even when the temperature in the room has reached the desired level.

To diagnose this issue, check the thermostat settings and ensure that they are correct. If the thermostat is not responding to changes in temperature or is not turning the boiler on and off correctly, it may be faulty and will need to be replaced.

Check that your heating system actually has a thermostat. In newer systems, such temperature controls are fitted as standard but in older systems, this is not always the case. I was once called out to a property by a lovely lady who had moved into a new home and did not realise that the property did not have thermostatic controls fitted.

Faulty or Dirty Diverter Valve

The diverter valve plays a crucial role in combi boilers by directing hot water to the radiators and other areas of the home in conjunction with the thermostat. It operates by opening halfway when the hot water tap is turned on in the shower or sink, allowing hot water to flow to the radiators.

However, due to its constant movement, the diverter valve can easily become stuck or clogged with sediment over time. This can result in the valve remaining open, providing the radiator with hot water even when the thermostat is turned off. Additionally, this can also lead to not receiving enough hot water in other areas of the home.

If you think that it may be the diverter valve, you may want to call in a heating engineer to take a look at it for you. They may be able to clean the unit or it can be replaced very quickly.

How to Prevent Your Radiator from Getting Stuck in the Future

Once you have found out what the problem is, you may want to look at preventing your radiator from getting stuck in the future.

Thermostats are simple pieces of equipment that can be easily installed onto any heating system with a minimum of fuss. Thermostatic valves will automatically turn off your radiator when the temperature in the room has reached an acceptable level and will allow it to heat up again once this has been achieved.

Alternatives to Radiators for Heating Homes (e.g., wood burner, heat pump, etc.)

If your heating system is on the way out and you are looking for alternatives to radiators, there are many other heating systems available on the market. Here are a couple of examples:

Wood Burners

Although wood burners are not as common in the UK, they are popular choices for many homeowners located in areas that receive plentiful supplies of wood. Wood burners radiate heat using convection, much like a conventional radiator but require regular loading to maintain temperature.

They can be wonderful alternatives to radiators in small homes – I personally have one in my living room and they are great at generating heat and producing a lovely aroma in the room at the same time!

Wood burners are now regulated so you will need to ensure that you get one that is compliant.

Open Fire

Another alternative to radiators is the fireplace. Although these are not traditionally used for heating a whole house, they can be great at producing heat and giving off a beautiful aroma in your home too!

A nice open fire would certainly complement a central heating system but I doubt it would be too good as a direct replacement.

Heat Pump

A heat pump is a device that transfers heat from one place to another without needing any additional energy. Heat pumps work on the principle of using electricity to transfer heat from a warm area (e.g., outside in your garden) to a cold area (e.g., your house).

If you are looking for a more modern alternative to radiators, heat pumps are worth considering.


In this article, we have looked at the ins and outs of how to turn off a radiator that is stuck on. There are many reasons why your radiators may be getting stuck on – TRV is not turned off, the thermostat is not installed properly or is malfunctioning, the valve sticking open due to wear and tear etc.

If you are looking for alternatives to radiators as heating systems, there are many other options available including wood-burning stoves (popular in some countries) and heat pumps which work by transferring heat from warm areas to cold areas without any need for additional energy input. I hope this post has helped answer all your questions about turning off your radiator!

4 Reasons a radiator won’t turn off Infographic

Plumbing Wizard Tips

“Make sure you check and double-check what could be the cause, you do not want an expensive bill for something really simple!”

“If you are still not sure what the issue is, you will need to call out a professional!”

“If replacement parts are required and you are unable to do this yourself, again… we recommend calling a professional!”

“We recommend having a TRV around 50% open and controlling room temperature with a thermostat!”

Frequently Asked Questions

How do you manually turn off a radiator?

Different radiators have different methods of operation but in general, all radiator valves need to be turned clockwise to turn them off. If this still does not work, check that the valve is in the “0” position (which means already turned off).

Why does my radiator turn off?

1) There is a high level of air in the system, and this number can be found by opening the low-pressure side valve on some radiators.

2) A thermostat might have gone bad or have dirt buildup on it, preventing it from properly regulating temperature and causing the radiator to turn off.

3) There may be an issue with your expansion tank being too full and not providing enough space for new water because either you failed to release air when filling your radiator or there isn’t enough room below the head normally reserved for air (due to debris build-up).

Why do my radiators keep coming on?

This is most likely the result of a defective thermostat.

It’s common for older homes to have a problem with faulty thermostats, however, finding and replacing an old thermostat is usually pretty easy, and it will often save money on both your heating bill and your house’s energy efficiency.

Why won’t my radiator turn off even though I’ve adjusted the TRV valve?

It may be because the TRV valve is not completely shutting off the flow of hot water, or there may be a problem with the lock shield on the opposite side of the radiator.

Can a faulty thermostat cause my radiator to stay on?

Yes, if the thermostat is not working correctly, it may be keeping all of your radiators on when you try to turn them off.

Can a dirty diverter valve cause my radiator to stay hot?

Yes, a dirty diverter valve can restrict the flow of hot water and cause the radiator to stay hot.

How do I turn off the lock shield on my radiator?

To turn off the lock shield, locate it on the opposite side of the radiator from the TRV valve, remove the cap, and use a tool such as a wrench or pliers to rotate the lock shield.

What should I do if my TRV valve is stuck and won’t turn off?

If the TRV valve is stuck, you can try using a wrench to loosen it, but if that doesn’t work, you’ll need to replace the TRV valve.

How do I know if my thermostat needs to be replaced?

If your radiators stay on when you try to turn them off and both valves are working fine, it may be a sign that your thermostat needs to be replaced.

How often should I clean my diverter valve?

It’s a good idea to clean your diverter valve at least once a year, or more frequently if you notice any issues with your radiator staying hot.

Can a stuck valve cause my radiator to overheat?

Yes, if a valve is stuck and can’t be adjusted, it can cause the radiator to overheat and stay hot.


Lee Pearce is not just a master plumber; he’s a veritable Plumbing Wizard. With over 30 years of experience in the trenches of pipes and drains, Lee has become the go-to sage for DIY plumbing, saving homeowners thousands in potential call-out charges. As the founder of Plumbing Wizard, he’s dedicated to demystifying the complexities of home plumbing, offering easy-to-follow advice that stands the test of time and pressure. His online blog is a treasure trove of tips, tricks, and tutorials that empower everyday individuals to take charge of their home’s plumbing health. Lee’s practical wisdom is not just about fixing leaks; it’s about imparting confidence and self-reliance. When he’s not writing or elbow-deep in a plumbing project, Lee is passionate about educating the next generation of DIYers, ensuring that practical skills are passed down and preserved.

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