Bleedin' Radiator only getting half hot mum!

[specialbeat]

Hello all you plumbtastic people.

I have a radiator that is only part heating up, does it need to be bled?
If so, what is the correct procedure to do this please?

Many thanks.

 

[jimbox]

bleeding is always a good start!

procedure:

1. buy a radiator key
2. have an old dishcloth or wad of tissue to hand to catch any water that dribbles out
3. insert radiator key
4. turn gently to open valve, allow any air/gases to hiss out
5. when water dribbles out turn key to close valve

if you are an irritating cowboy plumber: skip step 2, and replace step 4 with "turn quickly", and step 5 with "allow as much water as possible to **** out all over the carpet"

 

[specialbeat]

Hi there JimBox, thanks.
Huhmmmm, I don't need to switch the central heating off do I, whilst carrying out the job?

Thanks again.

 

[JPC]

generally not. (depends on system and how much air we are talking?

is it a gravity or pressurised system ?

 

[specialbeat]

Pass!
I have a back boiler if that's any help at all?

 

[JPC]

just bleed it then. will be tank fed from the loft

 

[specialbeat]

Thanks Jamie.
Do you think I should go around the house and attack all of the rads?
I say this not because they are neccesarily cold but cos some are noisy....bubbling sounds and the like?

Thanks.
Steve

 

[specialbeat]

Hello again.
Right, I tried to bleed the troublesome radiator and it took all night!
Basically I turned the key and air hissed out and after a few minutes the air stopped (still no sign of water), a few mins later, more hissing then stopped, it done this all night and it got to a point where I just left the valve open for a few hours...still no sign of water. I gave up in the end and the top and the middle of that radiator still doesn't get hot!

I thought I would have a go in the master bedroom to see what that was like (even though it didn't really need to be done because that seems ok) however, I seemed to experience the same thing.... a hiss of air then stop, no water, more hissing at intervals and no water. Next morning, that radiator is cold! Please Please help....have I not bled them right? Is there a correct order I should do this? Ahhhhhhhh! Thanks

 

[chrishutt]

You should turn the heating off when you vent. If the pump is on the return pipe it will create a suction effect which will make venting very difficult, as you discovered.

 

[JPC]

i hear what ur saying chris...but in practice i have not had this problem

 

[chrishutt]

Well you've been lucky. I find it quite a common situation when the rads in question are not much below the header tank and the pump is on the return, especially if pump speed is high. Negative head (suction)generated by a pump can be several metres!

Still, the poster can try it without the pump on and report back!

 

[specialbeat]

Hi there, thanks for the quick reply chaps.
Yes, just had a call from her in doors stating that most of the rads are cold now! Typical.....

Right, when you say turn the heating off, can I just put the thermostat down so it doesn't switch on?????

Also, is there an order I should do this?

Thank you kind people.

 

[Nige F]

You can turn the stat down so the pump stops.........also look in your loft @ the water level/ ballvalve working in the small feed tank...water`s got to get in to let air out Unless you`ve got a combi boiler

 

[specialbeat]

I don't think it is a combi Boiler.......it's a back boiler...that isn't a combi is it?
I'm sorry I don't have a clue about all of this!

Thanks

 

[JohnD]

there is a possibility that your feed and expansion tank is not topping up the radiators with water. this often happens with old systems, they get a blockage in the feed pipe.

Climb up into the loft and find it, make sure it has water in it and that the ballcock is working. See if there is sediment at the bottom. Mark the inside of the tank with a bit of tape or something, an inch higher than the normal water level, and press the ball down to get the water to this level. Then go and do some bleeding. This should make the water level drop by the amount of gas and water you have bled out. Go and see if it has.

If you have a total block, it will not drop at all.

If you have a bad but not total block, it may take hours.