How to Fix One Radiator Not Working – Plumbing Tips

Posted by in Plumber Talk, on March 7, 2018

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How to fix one radiator if it is not working. Includes the thermostatic radiator valve and lockshield. It also covers air in the radiator and sludge in the radiator. For more information visit

Hi and welcome to this weeks video.
Today I’m going to give you a bit of advice
About how to get your radiator working if only one’s working.
I’ve seen a few other videos on the internet about how to do this and some of them are plain wrong
and some could cause problems if you do it wrong.
Here’s the radiator in question, all the other radiators are burning hot,
the boiler’s on and the pump’s running,
and the thermostat in the room’s calling for heat.
but this one radiator isn’t getting hot.
If we feel the pipes feeding the radiator there is no heat at all.
and as I said all the other radiators are hot in the house.
so the first thing we do is check that the lockshield is open.
All you need to do is remove the lockshield cap.
You’ll find the lockshield valve here. Get a set of adjustables on there.
and open that fully up. Turn it all the way anticlockwise.
You never know, now you might find you have heat coming into the radiator.
to get the earliest affirmative answer as to whether there’s heat going into the radiator,
Instead of feeling the radiator at the bottom or the top, feel the two pipes going to it.
One will be a flow pipe and one will be a return pipe, and if now you’ve opened up your lockshield
and you feel one of these pipes getting warm then you know you’re getting flow.
However that might not have solved your problem, you could still have air in the radiators.
The symptoms of air in your radiators are quite simple to describe.
If you already have a hot flow and return going to the radiator,
If you’ve felt down the radiator and it’s warm at the bottom.
and at the top it’s cold,
This is always a sign of air being in the rads.
But before you go mental trying to bleed the air out of the radiators, I recommend you turn the boiler and the pump off.
Anyway, here’s how you bleed a rad.
Your boiler and pump are turned off.
Both radiator valves are open, although we haven’t checked the TRV yet, that could be stuck shut, we’ll check in a minute.
Get a little cloth
Get your radiator key in
Open that and as you can see we have water here already.
Obviously if the radiator has air in it you’ll have air coming out.
You’ll be able to hear a slight hiss and be able to control easily
The rate at which it comes out using this key.
As soon as you get water coming out just tighten it up.
Wipe up any water that might have spilt on the floor.
and then you should feel the radiator at the top getting nice and hot!
The next problem you can have is the TRV or thermostatic radiator valve is stuck shut.
Now this is where a few videos online have gone wrong.
Lets go over it slowly and if you follow our instructions you should get it going just fine again.
If not we have a quick guide on how to change a TRV.
Here’s the radiator valve in question. The first thing you need to do is make sure it’s fully turned on.
So it’s on setting number 5 out of 5. Next you need to be able to remove the TRV head.
There are a few different ways to do this, this one here is a screw on collar.
Some of the other ones by other manufacturers like danfoss
have a black plastic lug that you have to pop out to remove the head.
Once removed we can reveal the head and pin here.
This one I know works because I can puch it up and down.
Some of them the pin will be stuck down.
On this particular rad valve the best thing to free the pin is to
press on it and see if that will bring it up. The best way to be is gentle.
Don’t hit them with a hammer.
This type of valve wont have this problem but if you have a traditional pin type TRV,
If you hit it with a hammer, often the pin will just fly out and you’ll have lovely fountain of water come out!
the best way to deal with the pin type
is to get a small set of long nose pliers
and grip the pin itself
and you just wiggle it upwards and pull it up out yourself.
and that will get it working.
sometimes you’ll find once you’ve got it free.
You can push back down on the pin and it will stay stuck down,
at that point you will be looking at getting a new TRV for that particular radiator.
This particular type here because we don’t have that problem with it being a traditional type pin,
The best way I find to deal with these is to get a largish one of these, if it’s stuck down, like this and then slightly tap it
just to shock it, that’s all you need to do!
You’re not trying to bash the hell out of this so it moves,all you need to do is shock the tension out of
whats hold it in place.
Then it should pop up.

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