Radiator not heating

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sammya

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I have a radiator in the living room which has not been heating up for years. I've had a couple of plumbers checked this during the years & no permanent fix for this issue. I decided to do a bit of trouble shooting & find below what I've noticed & please suggest some fix.
The only way to heat up this radiator is to release air lock by disconnecting the inlet line (hot end). When this is done the radiator will heat up but the temp will gradually drop & the heating will stop in a couple of days. There is no issue with balancing. You can turn off all other rads this one will still not heatup. There is constant build up of air in this line alone.
I thought leak might cause the issue & closed the valve in the auto fill loop. The pressure hasn't changed in a week indicating no leak in the system (or a probable back pressure). Had a chat with a plumber & he recommends a expansion tank in the hot press and gave me a quote of €140+VAT. I have a mains fed close system with auto fill.
My question: Will this fix my rad problem & is this price OK. Is there anything else to check.
 
Hi, Is there an issue with the radiator itself - there might be a build up of "sludge" in there, or some in the pipes that affect the flow of water? Was the radiator taken off and cleaned out (garden house in one side, resulting "sludge" out the other side?
 
Try turning off all the other radiators and if possible shut off the central heating feed to the hot water cylinder coil. Select the fastest speed on the pump and run the pump for about half an hour. This can often clear air locks in the pipework feeding the radiator.
 
You may have a local pinhole leak or weeping valve.

Such could allow air into the pipes to replenish the air lock.
 
Forgot to mention, Yes I tried shutting all the radiators still no improvement. Also tried connecting a spare radiator still the same. The radiator was taken out & cleaned.The radiator will only heat up when air is released.
ONQ How to identify this without major damage.No visual leak noticed. I have wooden flooring everywhere in my house & if there had been a leak the fllor must have warped by this time. As I had mentioned earlier the pressure gauge in the hot press has been reading the same since last week. I shut the fill valve after releasing the air lock.
 
I'm at a loss sammya.

In general with a sealed system you will get some air in the water allowing a build up over time, but you're seems an unusual case.
Normally when I see this kind of air build up I suspect a leak - there's no more mystery than that. :)

If its not a system-generated fault then it looks like you might need to replace it.
Sorry I couldn't have been of more help.
 
There has to be an issue of air getting into the system as if you are releasing the air from the system and it is building up again within a few days it has to come from somewhere, and in a sealed system it can only come through fresh oxygenated water.

I would put my suspicions on the automatic filling valve. They are notorious for giving trouble and are also not good practice to install. I would certainly remove the valve and install a disconnectable filling loop or at least fit a lever valve (not a gate type valve) on the mains feed before the AFV. This way you will know for sure that the valve is not getting a supply of water and adding more oxygenated water to the system, hiding a leak or a weap somewhere on the system. Check again after a few days & see if there is a pressure drop.
 
But why does the air always get into that line. The are 10 rads in the house & only 1 has this problem. I was told that the auto fill valve is banned in some counties. I based in Co. Kildare & looks like this is not banned here. I'll keep an eye on the pressure & see what happens. I've had 3 plumbers to check the system & none had a clue. The last guy who saw suggested the expansion tank.
 
sammya said:
But why does the air always get into that line. The are 10 rads in the house & only 1 has this problem.
Click to expand...

Depending on how it is plumbed some radiators are more prone to gathering air than others due to there location and orientation of pipework. It probably has the easiest route for air to collect.

sammya said:
I was told that the auto fill valve is banned in some counties. I based in Co. Kildare & looks like this is not banned here.
Click to expand...

I would never install an auto fill valve. They are common practice as they hide leaks, therefore no call backs for the installer! It's the easy route.

sammya said:
I'll keep an eye on the pressure & see what happens. I've had 3 plumbers to check the system & none had a clue. The last guy who saw suggested the expansion tank.
Click to expand...

Do not install an expansion tank as this will definitely hide a leak if there is one. Best is fit a filling loop or a valve as I previously posted.
 
My recollection of a conversation years ago on this subject with a qualified plumber was that it doesn't just fix pinhole leaks it can gum up valves on the system, raise back pressure on the pump and generally cause more problems that it solves. Decouple yourself from a quick-fix solution and trace the cause, then get it dealt with competently.
 
I would not use leak seal in a heating system. It is a) very hit and miss as to whether it works or not and b) can cause problems as described by ONQ, especially in TRV's and motorized valves, etc.

If it were me, I would put a valve before the AFV or change to a filling loop and monitor the pressure for a few days. This will highlight if there is a leak or not. If there is a leak and it is not obvious where, then I would drain the system down, isolate the different zones and pressure test with air each zone to narrow down the location of the leak. Once this is determined, the high pressure of air can often be heard at the point of the leak. If not, the use of thermal image cameras and/or sonic listening devices can be used to pinpoint the exact location of the leak.
 
I've organised to connect a lever valve before the AFV & wait to see what happens. Thanks for all the replies. I'll get back with the results.
 
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