Upstairs radiators not working: 5 Steps to Take When Your Radiators Won’t Heat Up

Why is My Radiator Cold? | Common Problems

If your radiators feel cold or they’re not heating up sufficiently, you’ll want to understand why. While cold radiators could be a result of a more serious problem with your central heating system or boiler, there are a number of smaller faults that should be ruled out first.

Diagnosing your radiator problems

It can be frustrating when you can feel cold spots on radiators, particularly when you’re trying to get a room nice and toasty. There are a few factors that can cause cold patches in radiators. Here’s a list of common causes to review when you first discover a cold patch:

  • Thermostat is set too low
  • Timer isn’t working
  • Radiator valve is closed
  • Air pockets in the system
  • Blockages within the system
  • Circulation fault

Discover what to do if you boiler works but your radiators stay cold.

Why are some of my radiators not working?

If none of your radiators are heating up properly then there could be a problem with your central heating system or boiler. However, if some of your radiators are heating up while others aren’t, this could be one of a number of issues. Run through our quick fix checklist below to find out more.

Cold radiators in some parts of the home

If a radiator in your home isn’t getting hot, it may be due to a problem with one of the zones in your central heating system.

Central heating systems work by pumping a continuous flow of hot-water from the boiler to the radiators, then back to the boiler to pick up more heat. Within this system, you could create ‘zones.’ This means that you can control the temperature in separate areas of your home, depending on your heating requirements in each room. If you find that radiators are cold in one area, it could indicate that there is a problem with a particular zone.

One radiator not working

If you find that one radiator within your home stays cold, ensure that the valves located on the sides of the radiator are open. If the valves are open but the radiator is still cold, it’s possible that the valves are blocked. A suitable system cleanse conducted by a Gas Safe Registered engineer will usually do the trick.

Cold radiators upstairs

If the upstairs radiators in your home are cold, it’s an indication that the feed and expansion tank in your loft has run dry. This usually points to a larger problem. However, it’s also possible that the ball valve in the tank isn’t working correctly; it may be blocked or jammed.

Try the following:

  1. The cistern is usually found in the loft
  2. Clear any obstructions to the ball valve
  3. Refill the cistern, making sure there is enough room for the water to expand when the system heats up
  4. Refill the cistern so that there is just enough water to float the ballcock
  5. When the system is cold there should be just enough water to make the ball float and switch off the water coming in

It’s highly recommended that you seek the skills of a Gas Safe registered engineer when you have major heating or boiler problems. Remember that all boilers and heating systems should be regularly checked and serviced by a competent engineer.

With a full cistern, the upstairs radiators should start heating, but it’s a good idea to get a professional plumber in to work out why the cistern ran dry in the first place.

Cold radiators downstairs

If your downstairs radiators are failing to heat up, there could be a problem with your pump. If this is the case, it won’t be producing enough power to push the water around the heating system.

Pumps can get warm, but if it is hot or making a grating sound, then it might be about to break down, in which case it will need replacing. One of HomeServe’s Gas Safe registered engineers can provide help and advice to rectify this issue.

Why is the top of the radiator cold?

If the top of your radiator is cold, it’s possible that air is trapped within the system. Bleeding the radiator will release any trapped air, vastly improving the efficiency of your entire heating system.

Why is the middle of the radiator cold?

If the middle of your radiator is cold, there may be a build-up of debris or sludge which is obstructing parts of the bottom of the radiator. You’ll need to clean it out and remove all unwanted substances that are blocking the bottom length of the radiator.

If you have an open-vent system:

  1. Buy a heating system sludge remover at your local DIY store and use as per the manufacturer’s instructions
  2. Add the liquid to the feed and expansion tank
  3. After a few days you will need to empty and refill the system.

If you have a pressurised system:

  • You’ll need a plumber or heating engineer to help you
  • They will remove the radiator and flush it out to clean it
  • In some cases, your radiator will need replacing

Why is the bottom of the radiator cold?

If your radiator is hot at the top but cold at the bottom, there may be a build-up of scale, rust, or sludge which is obstructing the flow of water.

As with the middle of the radiator, if you have an open-vent system which is unpressurised and tank fed, you’ll be able to use a sludge remover to flush your radiator. However, if you have a pressurised system, you’ll need the assistance of a Gas Safe registered engineer.

Next steps

If you’ve managed to diagnose the problem with your cold radiator(s), the next step is to fix cold radiators in your home.

However, if you’re still stumped as to why your radiators aren’t working, our expert repairs team will get things working again in no time.

Tags: Boiler switch onRadiators and Heating Help

upstairs radiator not working – all others are ok – valve on one end Therm controller on other – took a spanner to valve and ensured open – still will not come on – what could the problem be?


9 Answers from MyBuilder Plumbers

Best Answer

photofinish contracts

Calne • Member since 6 Oct 2011 •

98% positive


On the thermostatic valve undo the ring which holds it onto the radiator, either by undoing the little screw or by unscrewing the retaining ring itself. Pull the valve off

and you will reveal a little silver plunger like a pencil lead about 1cm in size. Push this

plunger into the valve a few times to free it. The plunger getting stuck is often the problem. Then put the valve back together again. You should be able to feel the warm water coming into the rad as you waggle the plunger in.




Answered 8th Dec 2011


Boston • Member since 4 Nov 2008 •

100% positive

hi,there,s one way of finding out the problem,have central heating on and turn all working radiators off . .just leave the offending radiator on..failing that the trv valve is stuck in the off position,usually if you can remove the thermostatic top,no water will leak out..and just tap the spindle in the centre of the valve and off it goes..put the top back on..


Answered 8th Dec 2011


Rainham • Member since 3 Nov 2010 •

99% positive

Try taking the thermostatic head off and tapping the pin underneath. It is a very common problem that these pins stick. Have the heating on and keep tapping it firmly, but not too hard and you should find the rad getting hot.

Hope this helps.



Answered 8th Dec 2011


Chesterfield Mansfield • Member since 23 Mar 2010 •

100% positive

Pin stuck on thermostatic valve?


Answered 8th Dec 2011

RD Services Ltd

Milton Keynes • Member since 29 Nov 2010 •

100% positive

you could have an air lock. Turn all other rads off and this should shift air lock.


Answered 8th Dec 2011

crest installations and maintenance services

Boston • Member since 25 Oct 2011 •

100% positive


get a bleed valve key and open the bleed nipple at the top of the rad at one end,and let the air out .


Answered 8th Dec 2011

Concept building services

Sittingbourne • Member since 1 Jan 2008 •

100% positive


Is the radiator old? been in the property for years? could be a build up of sludge in heating circuit or a balancing issue turn the flow into other rads down a bit to allow circulation to extend up to the problem rad.

I would first try to bleed top problem rad,

Then i would shut a couple of rads off down stairs for the time being and check the problem rad to see if it improves regarding heat performance.

Allow a few hours to see if the heated water gets through to the upstairs rad.

I have seen this many times and it is just a patience thing in getting the heating system balanced.

If not get the system power flushed.

Try shutting off 2 lower floor rads first as this will allow distribution to by pass the bottom rads and deliver to rest of circuit reaching top rad.


Concept building services


Answered 8th Dec 2011

sovereign plumbing and heating

Walsall • Member since 23 Nov 2011 •

100% positive

Someties thermostatic valves jam shut call someone to free it off


Answered 8th Dec 2011


England • Member since 22 May 2019 •

100% positive

Please check under boiler ,flow or return valve someone messed partially open (not fully open) or (diverter valve faulty not fully open for heating, ) weak pump ,blockage on magnetic filter etc


Answered 28th Jan 2021

Why is my radiator cold – common problems and how to fix them


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It’s lovely when you wake up on a cold, crisp morning in a warm and cosy house, but if your radiators aren’t heating up as efficiently as they should be, you may wake up feeling a little bit chilly. There are a number of reasons why this can happen, from debris or air in the system to faulty valves. Below, you can find three of the most common cold radiator problems and how to fix them. 

Why is my radiator cold at the bottom?

When your radiator is cold at the bottom, it’s likely that there’s a debris blockage that’s restricting the flow of hot water to the whole radiator. Usually, the culprit of this particular problem is sludge, debris, rust and other bits of dirt. Over time, the metal that the pipes are made of can begin to disintegrate because they’re constantly subjected to oxygen and water. This combination causes the metal to rust and as this rust breaks off, it is carried around your radiators and pipework. If you live in a hard-water area, limescale can also build up in the system. All of these things together can cause a blockage. A small blockage can very quickly turn into a large one.

Generally, a radiator that is warm at the top but cold at the bottom suggests that the hot water is able to flow into the radiator but is getting stuck somewhere in the middle.

If it seems to be just one radiator that’s causing a problem, you can remove it and clean it thoroughly. Do this using a garden hose to remove as much dirt as you can, then refit it to the wall. If you think the problem stretches further than just one radiator, you can have the whole system power flushed. A power flush uses pressure to push water and other cleaning chemicals through the system, removing all the dirt and flushing it down an outside drain. This process is worth doing every now and then to ensure the system is running as efficiently as possible.

Why is one radiator cold when the heating is on?

One cold radiator usually indicates that either there is air in the system or there is a stuck valve within that radiator.

The thermostatic radiator valve (TRV), like the one pictured below, controls the flow of hot water to the radiator. From time to time, it can seize and get stuck, meaning that it cannot open to allow the hot water in when the heating is on. This is particularly the case in an old radiator.

To check if the valve is stuck, you can remove the rotatable head on the TRV to reveal a raised pin beneath it. You should be able to depress the pin with your finger. When you release the pressure, the pin should rise back up again. If the pin is already depressed or doesn’t move very easily, then this is more than likely your problem.

You can try to free the pin yourself using some pliers and grease until you can move it in and out with ease. However, you shouldn’t apply excessive force as this may damage the pin. If you are not sure about doing this or are not able to get the pin moving, then it is advised that you seek help from a professional.

If you’ve checked the TRV and it seems to be fine, there could be some air in the system that’s causing one radiator to remain cold. Air in the system tends to gather at higher points and prevents the correct distribution of heating water. Luckily, this particular problem is usually quite simple and straightforward to resolve with the following steps:

  1. Fully open all radiator thermostats and run the heating at full temperature for 10 to 15 minutes with all radiators on

  2. Turn the circulation pump off and wait until radiators are cool (around half an hour to an hour)
  3. Bleed the radiator nearest the boiler using a bleed key or screwdriver until water comes out
  4. Repeat this for each radiator
  5. Turn on the boiler and check the water pressure.

If you are unsure about bleeding the system or encounter difficulties at any point, it is advisable to contact a professional at the earliest instance.

Why are my downstairs radiators cold?

Cold radiators downstairs can demonstrate a balancing issue. Hot water tends to rise upwards in a system, so you’ll know you have a balancing problem if your downstairs radiators are cold and the upstairs ones are hot.

If this is your issue, go to the radiators upstairs and close the lockshield (the smaller valve at the opposite end to the thermostat) then open it a quarter turn. This should not cause any reduction in the effectiveness of the upstairs radiators, but will encourage more heat to flow to those downstairs.

If this doesn’t make enough of a difference, you may need to balance the entire system. To do this, you can follow our radiator balancing guide. 

Other things to check

If you’ve tried to do any number of the above, but you’re still experiencing cold radiators, here are some other things you can check.  

Check your boiler or heat pump

If your radiators are cold when you’re expecting them to be warm, you should check that your boiler or heat pump is working properly.

If you have a boiler, you should check that it’s on the right setting and working properly. For a combi boiler, check that it is set for both hot water and heating, is not in summer mode and that there is no fault code displaying. While some fault codes can be rectified by the user, others may require the help of a Gas Safe registered heating engineer. Always follow the user instructions and do not attempt to do anything yourself if you are unsure.

If you have a heat pump, you should check that it’s working as it should and that the outdoor unit isn’t clogged with leaves and other debris. You should also make sure that it’s not making any strange or unusual noises. 

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Check the water pressure

If your boiler or heat pump appear to be working correctly, the next thing to check is your water pressure. This is shown on a small display known as a manometer, usually located directly where the water supply is connected to your boiler.

For a residential gas boiler, the correct water pressure is usually around 1.0 bar, often indicated on the gauge by coloured markings. If the pressure is lower than this, we recommend following our guide to increase the boiler pressure. 

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If your radiators are cold at the bottom and hot on top, you’ll want to fix the problem as soon as possible. Not only are radiators that are unevenly hot not doing a proper job of keeping your home warm during cold weather, but radiators cold at bottom also waste energy, making your boiler work harder and your energy bills higher.

To fix the problem of half-cold radiators, you’ll likely need to learn how to bleed a radiator, and you may well also need your garden hose. At any rate, don’t ignore this problem – learn how to fix it before it gets worse.

Depending on what the problem is, you may be able to fix the problem yourself whether they’re upstairs or downstairs radiators cold at bottom. Fortunately, there aren’t that many variables where it comes to unevenly heating radiators.  

Jimmy Jackson, strategic HVAC Advisor at Texas-based and a master technician with over 25 years of experience, explains that ‘if one or two of your radiators are cold at the bottom, one of two things is the culprit.’

The first case scenario, according to Jimmy, is that ‘you may have air trapped in the radiator.’ To find out, ‘bleed the radiator. Locate the bleed valve. It should be on one side at the top. Place something under the radiator to catch any water that runs out.

‘Turn off your heat so that water isn’t being pumped through the radiator as you bleed it.

‘Slowly open the bleed valve. Trapped air will escape with a hissing sound. When the hissing stops, water will come out of the valve. Shut the bleed valve and you’re done. While you’re at it, you should bleed all the radiators.’

Air trapped in a radiator has an easy DIY fix. However, ‘if the problem isn’t fixed, you probably have accumulated dirt and rust (sludge) in the pipes. This will take power flushing by a professional.

(Image credit: The Radiator Company)

If you feel confident in your DIY abilities and know a bit about the different types of heating, you can flush out the sludge from your radiators yourself. Chris Harvey, a central heating expert at radiator manufacturer Stelrad , believes that ‘although a slightly messy job, this is something you can do yourself.’ Just remember to wear old clothes while you’re doing it. 

Chris recommends starting by ‘isolating the radiator by turning down the thermostatic valve. This should be turned down to Zero and make sure that you have locked the lockshield, this will isolate it from the system.’

The next step is the draining of the radiator. You’ll need to ‘place an old bowl on a towel under the radiator to ensure that all the water and the sludge are caught when it is released.’

A top tip from Chris when you are draining the water – ‘it is important to make sure that you turn the nuts on the radiator, this will help to make sure that all the water is fully drained.

Open the bleeding valve and bleed the radiator. Once all the water is gone, you can take the radiator off and take it outside. ‘You can then attach a hose to one end and flush out the radiator until clear water comes out the other side.’

After flushing, ‘you can dry the radiator off and you can then bring the radiator back inside and re-attach the pipes and nuts and bolts and wait for the radiator to fill, you should then bleed the radiator of any air to ensure that it is filled properly.’

(Image credit: The Radiator Company)

Whether you do the flushing yourself or hire a professional, this is a job that must be done if your radiators are cold at the bottom and you’ve established it’s not just air trapped in there. Even the best radiators will get clogged over time, but you are especially likely to experience this problem if you live in an older home.

Chris cautions against turning up your thermostat ‘to compensate for the cold patches. This won’t solve the issues and will instead increase your heating bill every month. ‘ This isn’t a boiler problem or thermostat problem, so you won’t solve it this way.

What is the quickest way to balance your radiators?

If you’re noticing that some of your radiators are a lot hotter than others, it may be necessary to balance them to ensure an even distribution of heat. However, Kimmy cautions that ‘there really isn’t a quick way to balance radiators. Radiators closer to the boiler heat faster. To balance them you adjust the valves on each radiator until they give a consistent temperature reading throughout the house.’

Realistically, this is a job for two or more people – according to Jimmy, ‘the fastest way to balance radiators is to have several helpers do it with you.’

(Image credit: The Radiator Company)

Can you bleed a radiator with the heating on?

The answer to this one is a straightforward ‘no.’ Gerald Carpenter, a professional plumber in the third generation and consultant on Sanitary Review , explains that
‘Before you start bleeding a radiator, you have to turn the heating off and
let the radiators cool down. Otherwise, the water will be too hot and spray
under pressure when you turn the valves. That’s something you definitely
don’t want to happen!’

So, heating off, old clothes on, garden hosepipe ready. Or, if none of this sounds like something you want to do, just call the plumber. 

Anna is Content Editor at Real Homes. She moved to the world of interiors from academic research in the field of English Literature and photography. She is the author of London Writing of the 1930s and has a passion for contemporary home decor and gardening. At Real Homes, she covers a range of topics, from practical advice to interior and garden design. 

Radiator Not Heating Up? Our Quick FIx Guide is Here to Help

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A radiator not heating up is a fairly common problem faced by homeowners — but it is a nuisance nonetheless, particularly if it is impacting more than one radiator in your home. Usually, there is a simple explanation and putting the problem right should not be too difficult.

So if you have found your radiators are cold and are puzzling over the cause we are here to help, with a list of the most frequent causes and their solutions. Some radiator problems will need to be fixed by a professional, while others are simple to put right on a DIY basis.

Why Are My Radiators Cold?

There are several probable reasons why your radiators are not not getting hot, including:

  • Debris in the pipework or filter
  • Circulation pump not working or has air in it
  • Air in the system
  • Thermostatic radiator valve (TRV) is stuck
  • Lockshield has been fully opened or closed
  • Boiler or heat pump not working properly
  • Central heating has turned off
  • Fuel source has run out

Here, we take a look at the possible reasons individually to help you identify which one is causing your cold radiators and explain what you can do to get them toasty again.

If you find a radiator not heating up, first check your central heating is on the right setting — it sounds obvious but it is a surprisingly common cause.  (Image credit: The Radiator Company)

1. The Radiator is Blocked

“If the system has not been serviced then there could be a build up of debris in the pipework or the filter,” explains David Hilton, Director at Heat and Energy Ltd . The simple solution is to get the system serviced by a professional.

Blocked radiators can be caused by a build up of limescale, sludge, rust or debris flowing through the system. This restricts the flow of water meaning blockages that start of fairly small can quite quickly become big blockages. 

Blocked radiators are usually cold at the bottom and warm at the top.  

If the problem is only affecting one radiator, it can be possible to remove it and flush it out with a garden hose, before replacing it. However, if you have several radiators not heating up then it may be necessary to have them power flushed by a professional.

A power flush uses pressure to shoot water and chemicals through the system, removing dirt and flushing it away down an outside drain. 

2. The Circulation Pump is Not Working

If a few, or all, of your radiators are not heating up, the circulation pump could be to blame.

Circulating pumps move hot water around a heating system, taking it from the boiler through the pipes to your radiators and hot water cylinder in some cases — before taking it back to the boiler. 

Sometimes, blockages or airlocks in the system will occur. Good indicators that this may have happened, other than radiators not heating up, include a water leak from the pump, unusual noises coming from the pump, casing that is hot to touch and no hot water. 

You will need to call in a plumber to fix the problem.

3. Air in Heating System

A very common cause of radiators not heating up is an airlock in the central heating system.

“There could be air in the system which would mean that the radiator may only heat a little bit at the bottom, or not at all if there is a lot of air,” explains David Hilton. “You will need to bleed the radiator to get the air out. 

“As you let air out of the system you need to allow more water in. A gravity fed central heating circuit should fill automatically but a high pressure system will have a valve (or two) to let the water in. Don’t leave this valve open. Pressurise the system a bit and then bleed the radiator. It is usually best if two people do this but if in doubt call in a professional.”

Sometimes it will be necessary to bleed your radiator to get rid of an airlock.  (Image credit: Getty)

If it is just one radiator not heating up, then a stuck thermostatic radiator valve could be the culprit.

A thermostatic radiator valve (TRV) controls the flow of hot water to a radiator and occasionally these can get stuck, meaning they can’t open to allow the hot water in.

“The TRV pushes a pin in and out and sometimes this pin corrodes and will not move,” says David Hilton. “By unclipping the TRV you may be able to free it up, but be careful as it may be badly corroded and pop out or leak.

Try to free the pin using pliers and grease but don’t use excessive force as you might damage the pin. If you can’t free the pin then we would advise you call a professional.

5. The Lockshield is in Wrong Position

“On the opposite side of the radiator to the TRV is a lockshield,” says David Hilton. “This looks like a small valve with a cap on it and it is used to balance radiators. What can often happen is that this is closed when a radiator is moved (for example, to paint behind a radiator) but then fully opened again when the radiator is replaced, rather than returning it to its previous position —  which is often only a quarter turn open. 

“This means that the boiler water will now circulate more through the closed radiators and hardly ever get heat to furthest away radiators.”

A good signal that this is your problem will be if the radiators upstairs (or those nearest to the boiler) are getting hot but the downstairs radiators are cold. The system will need to be rebalanced.

If you find that your radiators upstairs are hot but are cold downstairs, your lockshield may be in the wrong position.  (Image credit: The Radiator Company)

6. The Boiler or Heat Pump is Not Working

An obvious reason for radiators not working is a faulty boiler or heat pump. Check your boiler is on the right setting and appears to be working  — a fault code will usually alert you to a problem. You may find you can put it right easily, but in some cases a Gas Safe registered heating engineer will need to be called out. 

If you use a heat pump to heat your radiators, check it is working as normal and that it hasn’t become clogged with any debris. 

In some instances, you may need a new boiler. For a free boiler quote, visit

7. The Water Pressure Has Dropped

If you have a combi boiler, or a high-pressure central heating system, the problem could lie with a drop in pressure, causing the boiler to cut out.

Take a look at the pressure dial — it should be in the range specified in the instruction manual. If not, you will need to top-up the water (check your manual for instructions) to repressurise the boiler.  

Check the pressure on your boiler has not dropped — this is a common cause of radiators not heating up properly.  (Image credit: Getty)

7. The Central Heating is Off

Yes it sounds obvious, but before you do any of the above, you really should check that your central heating hasn’t been switched off or set to summer mode, or to heat the water only, by accident — you really don’t want to go calling out a plumber only to discover this was the cause. 

8. Running on Empty

Another embarrassing cause of radiators not heating up (a bit like running out of petrol). 

If you use LPG or heating oil to power your heating system, could it be that you have forgotten to check your fuel levels and run out?  

One issue here is that running out oil can result in debris in the tank entering the heating system. Your system might need power flushing by a professional as a result. (So the bottom line is, regularly check the bottom line on your oil tank to ensure you don’t run out!)

Natasha is Homebuilding & Renovating’s Associate Editor and has been a member of the team for over two decades. An experienced journalist and renovation expert, she has written for a number of homes titles. She has renovated a terrace and is at the end of the DIY renovation and extension of her Edwardian cottage. She is now looking for her next project.

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2 Upstairs Radiators Not Working…. 🙁 sooooo cold!!!!