Radiator won't bleed

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usrbin

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I have a weird one, I think...

A radiator upstairs that needs bleeding - well, it warms at the base but remains cold at the top - yet when I open the bleed valve I get some escaping air (hiss) followed by... nothing. Silence. And no water.

I've given it ten minutes but nothing's coming. What could be causing this (low water pressure)? And how to fix it?
Thanks
 
Not enough water in the system, Open the feed valve for about 10 sec, close it and then re do the bleeding and water will flow. Have to do this myself maybe twice a year.

secman
 
Ah, very good, makes sense, thanks very much secman. Please excuse my ignorance - do you meanm the feed valve on the individual rad itself? Or is there a "central" one on the boiler or elsewhere?

(You have to do this twice a year? Does that mean you have a leak?)
 
There should be a valve to top up / feed the heating system, mine is in the hot press.With regards to having to do it twice a year, I asked the same question about a leak, but my 2 brothers both of them being plumbers have searced and there is no visible sign of a leak. Apparently the heating system doesn't hold as much water as we would believe it to. ie in the rads and pipework, the rad I have the problem with is in an attic conversion and it being the highest point on the system, this is where the air rises to. They have put it down to this and that its only the natural air in the water rising to the highest point in the attic. They say that if i had a leak that I would be topping up the system on a daily basis and not 2/3 times a year.

yours

secman
 
If your filling loop is beside the boiler keep an eye on the pressure gauge when you top up the system, ideally you want it a 1bar when its cold as water expands when its hot and you won't get an accurate reading. If its like Secman's and in the hotpress, open valve for very short period and keep eye on the pressure. If the pressure is slighty high don't worry as pressure will drop when you bleed rad.
 
this thread caught my eye! I've a wierd problem as well. so if anyone has any suggestions, i'd be grateful!

3 rads downstairs, 2 heating perfectly, 3rd is tepid at the bottom and cold at the top. 4 rads upstairs, one heats perfectly three are again tepid at the bottom, and cold at the top... I've tried bleeding all rads, but no air escapes, just drip of water, at which stage I obviously close the valve again.

Anyone got any ideas? The rads that do heat are great having said that, so I'm totally bewildered!!!

Thanks

EB
 
Could be one of two things, the system has sludge in it or more likely that it wasn't balanced. the rads closet to the boiler and pump heat up fastest. i would turn off the rads that are heating and see if the cooler ones heat up. you only need to turn off rad valve one side. when the cooler ones heat up turn back on the rads but not fully, just a couple of turns. this will limit the amount of hot water passing through the hotter rads and help the cooler ones get more hot water. also I would look at the circulating pump and see what its set at, they usually have three settings, low medium and high, turn it up if its low.
 
I have a similar problem, but can't follow the directions already given.

The system is approx. 18 months old. The immersion tank is in the garage and there are a load of pipes and valves around it. The system is gas-fired and the gas boiler is close to the immersion tank so it's hard for a tool like to track what is what.

Is there a foolproof method for locating the feed valve ?
Also, should this be done when the heat is on or off ?

Also, it is the bathroom heated towel rails that are the issue - the radiators are all OK.

Thanks
 
We've had exactly the same problem with our heating system. Luckily the house is only just a year old so I went back to the builders and made lots of noise. They sent someone out to sort it.

There was a very small leak in the system actually under the boiler. It was only by chance that I spotted it. It was leaking hot/warm water that ran down the back of a hot/warm pipe and was therefore evaporating before becomming very evident.

Might be worth another look over all the pipes / conections Secman...
 
TarfHead said:
Is there a foolproof method for locating the feed valve ?
Also, should this be done when the heat is on or off ?
Click to expand...

It is attached to the mains water. It will be a black knob. The pipe will only be 1/2" leading to (in most cases) a larger 3/4" or 1" pipe. The larger pipe will be hot when the heating is on but this smaller pipe will remain cold and get very cold when you open the valve a bit to let the water in. There will be a small guage showing 1 to 5 on top or very near the valve.

If your really stuck post a picture of some valves and gauges you have.
 
Hi
I just had this problem. The ballcock in the central heating top up tank had stuck closed. Once unloosened it filled the tank and I could bleed the radiators as normal. Check to make sure the ballcock valve shuts off as normal after it has filled to level.

Hope this helps
 
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