/ Home & Energy

Are your radiators on yet?

It was National Radiator Day yesterday (yes, such a day exists), so come and share your hot tips on how to keep your radiator snugly warm throughout the winter. That’s if you’ve switched them on yet.

From clunky cast iron to sleek white, how do you make sure your radiator stays in toasty tip-top condition?

And how often is it necessary to do those essential jobs like bleeding your radiator? Once a year, twice a year or perhaps never?

Bleeding your radiators

The first time it ever occurred to me that a radiator would need ‘maintaining’ was when I was a student. I had a big draughty room and a tiny, inefficient radiator. The room was freezing and by the time December came around I was wearing a hat to bed.

After many grumpy phone calls to my landlord complaining that the radiator needed replacing, the handy man came round and within two minutes my radiator chugged in to life. I marvelled that with the magic of a little key, I had the joy of fully-functioning central heating.

Clearly it’s best not to leave it that late – in fact now’s probably a good time of year to bleed your radiators before it gets too cold (to release trapped air).

Nowadays I’m lucky enough to live in a house that has under-floor heating. At this time of year it’s a real treat, rather than faffing around finding radiator keys or dealing with inefficient chugging radiators, I can just flick a switch and wait until my toes are nicely warmed by the floor boards.

Radiator maintenance tips

I’ve also discovered, thanks to National Radiator Day, that there are a few other tips that I can do to keep my radiators running efficiently throughout the winter. Things like dusting the convection fins (the zigzagging metal strips on radiators) and rearranging furniture to help airflow. It’d be interesting to hear if you have any other tips on how to keep your heating and radiators in tip-top condition.

So, have you bled your radiators yet? Oh, and don’t be shy about sharing your radiator disasters – have you virtuously tried to flush your radiator of gunk only to have radiator sludge ruin your carpets?


My hall radiator always gradually accumulated air and had to be bled. Fortunately this radiator is easily accessible and the job took little time. I did fit an automatic vent which has worked well for years. It’s a good solution for anyone who has air accumulating in a radiators that are not convenient to bleed.

Heating on? Already? You’ve got to be joking!

I can see why yesterday might have been NRD though: it was officially the first day of the Public Buildings Heating Season (in the UK) ….when we were sensible enough to follow such things and not have heat all year round.

My heating is NEVER on before the start of Public Heating Season and NEVER after the end either.

I have, though, had the gas fire on in the lounge a few evenings last week, but it’s warmer again this week up here.

“Onesies” have become trendy .. and after being rather sceptical and thinking they were a stupid fashion craze, I’ve bought one from the all in one company limited and it’s FANTASTIC. I can see me using the heating less than ever this year! Maybe which? could do a product test on onesies?

P.S. – forgot to say, only times I have ever had to bleed any rads since the heating was installed in 1979 have been when I’ve drained all or part of the system, such as taking a rad off to decorate, having a rad replaced (just the one) or when the boiler was moved when the workshop was built. In between times I seem to have been incredibly lucky and never ever had to bleed any of them.

Flushing the system is easily done using the system drain c**k that is supposed to be fitted at the lowest point of every system and has a hose tail on it to connect to a garden hose taking the dirty water outside. Got to say I rarely do this – I rely on Ferronox inhibitor in the system as recommended by the plumber who services the boiler each year. Seems to work – 33 years for a boiler and all but one of the rads can’t be bad.

It does depend on where you live .
Have had the heating on for a 2/3 weeks now, as I do feel a temperature of >18C is necessary in the occupied rooms and with outside temperatures struggling to hit 10C that isnt going to happen without some help !!

Usually check for seepage from the radiator/valve joints and top up the inhibitor during the summer.
Always a good idea to exercise all the valves as well – it stops them seizing up.

@rarrar – very true, though personally I could not stand 18 or higher indoors (unless I’m going to walk about starkers!). My heating has always been set to 15 which is just about right for me, though on very bitter winter mornings getting undressed for a shower can be a little chilly at 6 a.m.!!!

I think we’re quite lucky here in South Yorkshire – we don’t often seem to get the bitter cold of the Pennines, even though I am barely 8 miles away from the start of the Pennine Way. We do get all the East-Pennine rain though! 🙁

Oh dear .. Which? profanity filter doesn’t like plumbing terms .. drain c**k was what I tried to type above. I won’t even test it with gas n1pp1es and ba11 taps!

My boiler, radiators and pump are all about the same age as Dave’s and are working fine. I have Fernox in the system too. Rarrar makes a good point about giving radiator valves exercise to prevent them sticking. Despite this, I have had to replace several thermostatic valves.

Anyone whose water is heated by gravity should run the pump every week or two over the summer months to prevent it seizing or silting up. That should not happen if the pump is sited correctly but some installers ignore the recommendation and mount pumps horizontally at the lowest point in the system.

I don’t like ‘National Radiator Day’ because it seems to be promoting one company’s product.

My boiler and I assume many others have a pump exercise function built in this spins up the pump and activates the CH diverter valve once every day if unused.

Hello Dave, believe it or not, we’re all sitting in Onesies in the office right now. 😉 And sorry about the profanity filter, but I’m reticent to add your word to the ‘safe’ list, as in other contexts it can be rude. Thanks.

No worries Patrick – I don’t seriously expect Which? to mark C**k as acceptable as it is likely to be abused.
My plumber and I do, however, have regular conversations about how crazy it is that in order to be politically correct plumbers’ merchants are no longer supposed to use the three words I alluded to, which is mad given that they are the technically correct words for the items.

DELIGHTED to hear the Which? team are in onesies! When’s the review / report on them and when do we see a pic of you all wearing them in the office?! Great news – see how much Which? saves on heating the office this year! (No, I know you won’t really all be wearing them all season!)

Good job you dont live in the recently flooded town of C###ermouth .
I failed to set up Yahoo accounts for a couple of organisations there a few years ago just wouldnt accept the name even as a username !

@rarrar ….. Scunthorpe council had a similar problem several years ago …. dunno if that will pass the filter.

However, we digress ….. this convo is meant to be about heating rather than profanity filters. We’ll get told off by the top cat in the onesie 😉

Ahem. If you say draincock as one word you should be fine – though the mispelling might wind you up. My radiators haven’t been turned on this side of the year yet… I quite like the cold fresh air and have the window open. We’ll see how long that lasts.

Nice one Patrick – someone else who likes fresh air and ventilation! Shame there are not more people who think the same way in many stuffy offices up and down the country.

Sophie Gilbert says:
3 October 2012

I have a gas central heating system that is well over 20 years old and gets serviced once a year every year and neither I nor the engineer have had to bleed the radiators once since I’ve lived in the flat, since 1998. A friend of mine had gas central heating installed in 2002, supposedly superefficient, and his radiators need to be bled all the time. That’s one of the reasons why I’m reluctant to part with my old cracker of a system, I may use more gas, but it just ain’t broke.

I would not replace the system either. New boilers may be more efficient but have a reputation for unreliability.

It is good that you don’t have to bleed the radiators but it is generally very easy and quick to do.

If they need bleeding a lot then either air is being sucked into the system, gas is being generated due to lack of inhibitor or you have a leak and are constantly adding new “gassy” water to the system from the header tank if you have one.

Thanks for the suggestions, rarrar. I had the same thoughts when I moved in to my house 30 years ago, but I never managed to find out why my hall radiator needed to be bled every month or so.

The system had inhibitor and I have replaced it twice without any change. If part of the ‘air’ in the radiator is hydrogen produced by corrosion then there is not enough to burn, and there is very little sludge in the radiators. I am losing little water because I can turn off the header tank supply for months and it does not empty. It is a mystery but fitting an automatic bleed valve to the affected radiator means that it no longer needs to be bled.

I hope that your suggestions might help someone else.


My parents’ bedroom radiator always filled with air very fast from the day it was installed in 1969 until long after my dad died when in 2005 my mum asked the plumber who services the boiler every year about it.

The plumber explained that air will get sucked INTO the system through pin-prick holes or microscopic gaps in thread-seal which are too small for water to leak out.

He looked at the affected radiator and decided that right from day one the blank plug in the top of the rad at the opposite end from the bleeder has not been tightened quite as far as it should.

A quick nip with his spanner and, 26 years after installation, all the air gathering stopped like magic!

It just could be that your hall rad (or a pipe joint very near to it) has such a microscopic ‘leak’.

Dave D

Thanks for the suggestion. Air can certainly be pulled into a CH system when the pump is running.. My parents’ upstairs radiators could not be bled unless the pump was switched off, and opening the bleed screws would pull in air.

I’ve given up trying to fix the problem and my one automatic bleed valve keeps the offending radiator full.

I suppose it depends a lot on where you live. It hasn’t been *too* cold here in London yet so I haven’t put mine on. I’m usually a bit unhappy about putting them on at any time before November, as I’m really tight with my heating bills!

I’ve bled the ones that needed doing quite recently, but I didn’t realise that dusting the convection fins could make a big difference, so I’ll have to go round and have a quick clean-up!

As long as the radiator is giving out enough heat to warm the room then dusting and bleeding are not necessary
They don’t make the radiators much less efficient ( i.e. wasting heat) , they will just have a lower output.
Wearing thicker clothing , getting used to a lower temperature ( difficult when many offices are over heated) and only heating the rooms is use will make a big difference in heating costs as does being “at home” less.

Gerard Phelan says:
4 October 2012

I like my living room to be about 21C/71F, which it will not be in current Surrey evenings without assistance. Since my boiler flue was recently condemned I am waiting for a new boiler system to be installed at the end of October and noticing the cold.

In the meantime I am having to relearn the purpose of a cardigan and get annoyed at the noise made by a electric fan heater. I am assisting with a dehumidifier, since dryer air will also feel warmer and the dehumidifier also contributes its waste heat and noise. It will be interesting to see if the new system requires more radiator maintenance. My old one never needed any radiators to be bled in 20 years.

Durelli says:
4 October 2012

I see a couple of references to adding inhibitor to the CH system.

How easy is this to do? I thought this was more for a plumber to do when fitting radiators etc?


It is not necessarily difficult but you will need to do a bit of reading and some preparation, such as flushing the system. Inhibitor is best added to a new CH system, following the instructions carefully.

It is well worth doing because without inhibitor, steel radiators will gradually corrode internally and fill with black sludge that can make them less effective and cause problems with circulating pumps, etc. Black sludge can make a horrible mess of carpets if radiators have to be removed or start leaking due to corrosion.

It is important to record what inhibitor has been added because topping up with another brand could cause problems. Label the system with what has been used and when it was added.

We had a problem for several years with “air” accumulating in an upstairs bathroom radiator which did indeed prove to be hydrogen.This was demonstrated with a lighted match applied to the loosened bleednipple when the gas burned with the characteristic pale blue flame.(about one inch long-take care- have a damp cloth ready!). Draining the system and refilling with corrosion inhibiter added to the loft header tank stopped the generation of hydrogen. A complete refill does of course introduce a lot of new dissolved air and this will need to be bled off a few times and may take weeks. It is unwise to allow air to stay in a steel radiators as this also promotes corrosion.

Insurance companies insist that heating systems are drained down in several instances where property is left unattended. Obviously flooding of the building is their concern. The problem is, as confirmed by my experienced plumber friend, the radiators quickly rust from the inside in the absence of inhibitter. Additionally, if drained down, the inhibitter, which if of good quality is expensive, must then be replace on refilling the system.
My solution is to shut off the water supply and drain the tank but to close every radiator at each end and leave the heating system undrained. I believe that this should limit damage in both the long and short term.
Should a leak develop, it is likely to be small and damage might even be averted by evaporation!
Many people take longish holidays and I wonder what proportion act on the Insurer’s instructions.
Can any expert tell me if i’ve judged the odds correctly?

I’m not an expert, but here are my thoughts….

I suggest you buy a combined corrosion inhibitor and antifreeze, or find an antifreeze that is compatible with the present inhibitor.

Me and many others waste energy by leaving the central heating to come on if the temperature falls below 5 or 10C.

You also need to consider what to do about the hot and cold water system. Even a small amount of water left in a pipe can freeze and cause a burst. Obviously if the water is off at the main, the possibility of flooding is less.

Isn’t this why most people take holidays in the summer? 🙂

Helen M says:
12 October 2012

Is it worthwhile to fit heatkeeper radiator panels? Do they really keep the house warmer?

You will find cheaper products that will do the same job but I have no idea if they will make much of a difference. If they did, I think they would be recommended more frequently.

My heating is never switched on before Bonfire Night and always goes off on or before March 27th. I really don’t know how ‘ordinary’ people can afford to heat their homes from late summer to late spring, especially with thermostats set in the mid twenties. My thermostat is set at 15 degrees, and the heating only comes on for four hours in the evening during my ‘on’ period. The general temperature in my house during late autumn and winter is 12-13 degrees. Yes, it’s cold, but a couple of cosy blankets when watching tv and a couple of hot wheat packs in the bed to warm it up, and I’m absolutely fine. In fact, now that the cost of gas and electricity has risen even higher, I think my ‘on’ and ‘off’ dates are going to have to be brought closer together. I keep reminding myself that as a child we didn’t HAVE central heating, and it was quite normal to have to scrape thick layers of frost off the INSIDE of the bedroom windows to be able to look out to see what the weather was like. We had a little coal fire in the living room and that was it. Plenty of warm clothing did the trick. I get fed up with people who expect to wear summer clothing (strappy-tops and thin T-shirts) and then complain that they’re cold. PUT SOME WARM CLOTHES ON AND PLENTY OF LAYERS!!!!! You CAN teach yourself to cope with colder and colder temperatures. Drop the thermostat a degree at a time until you adjust and before you know it you will also be one of those who copes with almost no heating. Gas is running out, and so is my money – I don’t feel I have any alternative and it doesn’t harm me. A good walk out in the fresh-air is very warming, and the house feels toasty to come home to, even if it’s only 12 degrees inside!
So in summary:
Give yourself EXACT on off dates for your heating
Progressively lower the thermostat
Buy long sleeved vests and long johns
Get some hot water bottles or hot wheat packs
Wear multiple layers
Get fingerless gloves for wearing at the computer.
Go for a walk when you get too cold.
Keep reminding yourself that people have lived in the UK for thousands of years with no heating and survived, and to stop being such a namby pamby.
Remember that gas and electricity cost money: if you had to pay for it in advance, would you use so much?

Regarding radiator panels, they absolutely do make a difference. I hate feeling cold and have a big open plan space downstairs which wasn’t warming up very well. I read that you can lose alot of your radiator heat through the wall behind and reflectors will direct this heat back into the room.
We bought Radflek which is REALLY simple to use and assemble… just cut the reflective sheet to size ( it doesn’t even have to be that exact), attach the plastic hanging clip on each side and drop behind the radiators! We’re much warmer downstairs and have been able to turn the thermostat down.

Helen M says:
31 October 2012

Thank you, Rachelle. A great help.

Ronnie Clayton says:
14 December 2012

Hi could you tell me how to keep the rads downstairs warm the ones upstairs seem to stay warmer longer than the ones downstairs when the pump has gone off do they need ballancing

Regards R Clayton

Do you have 8mm or 15m diameter piping to your radiators? How many radiators do you have? What is the boiler output? Pumps usually have 3 speeds. Is yours set to maximum speed?

derek says:
16 January 2013

Reading various items re the cold – i think an important tip is to ensure your radiators are ample for the room size. I moved into my present bungalow, discovered the living room TRV never shut down at required temp. when I used a room btu calculator i found instead of a single panel single convector i needed a double panel double convector radiator. changed it for 80 quid and now my living room is nice and toasty. which in turn is saving me money – I aim to size all my rads for my rooms to ensure they are adequate – hope this info helps

Derek, I completely agree and it is quite easy to do as radiator output (in Kw or BTU) is readily available from plumbers merchants.The other thing to watch, particularly for those folk with “microbore” systems , is pipe diameter to radiators.As a guide ( from “The Which? Book of Plumbing and Central Heating” published in 1994) 8mm diameter is sufficient for radiators up to 1.5 kw output but 10 mm is required for up to 2.5kw.However, from personal experience 8 mm is no good if the distance from the main 22mm pipework is longer than 3-4metres.10 mm pipes are OK to supply a 2.5kw radiator for up to 6 metres away from the 22mm main pipes.15mm pipework will provide up to 6kw ie sufficent for 2 or 3 radiators.For completness, 22mm diameter primary pipework can supply up to 13kw and 28mmm diameter pipework can supply up to 23kw.Don’t be mislead by plumbers that want to replace a small radiator with a large radiator and not replace the pipes that are too small!

Jacqui says:
12 June 2013

We are having our 30 yr old boiler replaced with a Worcester Bosch – we have the old cast iron Victorian radiators. If we change our radiators to new radiators, will we save money? I know cast iron takes longer to heat up, longer to cool down – but is there any proof that new ones will save me running costs? Heeeeelp – I cannot find an answer and need one before the workmen arrive!

If your existing boiler is still in serviceable condition and reasonably reliable, I suggest you keep it. New boilers are more efficient but many have found them unreliable and expensive to repair.

I cannot comment about the radiators but you could find that they are worth money if they are very old and in reasonable condition.

Hello Jacqui.

Sarah from Which? Local, here.

I’ve posted your comment in our forum here.

Our community includes a number of central heating engineers so keep an eye on the thread for updates!

Jacqui says:
12 June 2013

I don’t want the answer to be about the boiler, costs of rads etc – just is there any proof that new rads will save me any heating costs over old victorian radiators? Cannot find an answer anywhere so do not know whether to change them – I have new rads ready and waiting, cost me very very little.


I cannot see any scientific basis for a difference in costs. There may be a difference in how quickly they warm the rooms, but the same would apply if you compared small and large radiators. Here is a link to what looks like reasonable information. I know nothing about the company and the page just turned up using a Google search: https://www.castrads.com/frequently-asked-questions/buying-cast-iron-radiators/are-cast-iron-radiators-as-efficient-as-modern-radiators/

If someone has sold you new radiators on the basis that they will save money, I would be very interested to see their explanation.

Jacqui says:
12 June 2013

Bought rads at auction, will be able to sell again for profit – my business works on this premise, so no hardship. The link was extremely usefull! Many many thanks. Jacqui

I think you could possibly find that the new boilers simply cannot heat up the old rad’s in a reasonable time nor keep them properly hot in very cold weather. New boilers are actually not at all efficient unless installed in very specific ways with very specific heating system components. I’m not a boiler engineer but my highly respected plumber and heating engineer tells me, and I’ve heard it said on consumer programmes like You and Yours and Watchdog, that new boilers will only work efficiently or effectively if they are installed into “ideal” systems.

Therefore I suspect that the answer to your question is that new rads alone are not more efficient and that the new boiler alone is actually very inefficient, but if you replace both boiler and rads you **might** manage to achieve a slight efficiency saving and maintain a reasonable heat-up time.

Wavechange’s original answer, which you did not like, is actually the best advice: don’t change the boiler. Your new one won’t be designed to last more than 8 years, and quite possibly won’t even do that long, it will be unreliable – especially heating up old style rads – at the side of the existing one and could end up costing you far more to run than your existing one.

Even the boiler manufacturers openly admit that you will never save enough on gas in the boiler’s life time to cover the cost of having it put in; you’re on to a loser if you are doing this to save cash.

If you have no choice but to replace it then I think you might well need to replace the rads too to avoid multiple future failures.

Hope this helps.

We have started to have a major problem with our radiators,
We have 8 radiators in our property and we have found that the upper level of the house warms up really quick but the lower level doesn’t.

We have tried the bleeding of radiators with no success, so we are now considering a power flush of the full system!

Sounds like your rads need balancing, not flushing.
Have you had any changes made to the system lately? If so I’d bet my bottom dollar on it needing balancing.
Power flushing is just a rip off an often causes leaks.

Claudia says:
30 December 2014

I find that cast iron radiators to be the most cost-efficient: they stay hot about one and a half hours after the boiler has been turned off because unlike modern steel radiators they retain the heat beautifully. Ours date mostly from 1920s, 30s and 40s. Modern versions tend to be much more expensive. All of our downstairs raditaors are second-hand cast iron (American Radiator Company (pre-1929) and its subsequent name Ideal (post 1929)). We have mostly picked these up in Portobello market and junk shops and have cost on average £25 a piece. Of course we have then had to test, sand and repaint them but so far they have been fine. Mostly they have been removed recently from houses so the valves have been the right ones.