Hoping you can help. We have replaced the radiator in our upstairs bedroom due to previous one being cold. The new one was toasty for a month but now the wheelhead valve side pipe is cold but the lockshield valve side pipe is hot. This water seems to be backfilling into the radiator and it can be warm/hot to touch but not giving out any real heat. I have turned of the lockshield valve and opened the bleed valve at the top and water was getting pumped through which was clean but cold. We balanced the system yesterday but the problem persists. The pipes are 8mm and not sure how old the CH is but when we replaced the rad a lot of black granules came out of it. Last year we took the old rad off and flushed through due to no heat which fixed the problem until last November. Any ideas on why the wheelhead pipe would be cold would be greatly appreciated.
Replace radiator was hot for 1 month now cold
- Thread starter ElizabethR
- Start date
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If one side of a rad is hot and the other cold, then clearly the water isn't going around it. Either it is sludged, you have a faulty valve or an air lock issue. You seem to have discounted the latter, so.....
You say you have already seen some sediment in the system - that it pretty normal unless it has recently been cleaned out, but have you tried taking off the rad, flushing it thru? Also, while off, try undoing the two valves, one a time (very slightly cos you dont want to flood the room!) to see if they are opening properly.
You say you have already seen some sediment in the system - that it pretty normal unless it has recently been cleaned out, but have you tried taking off the rad, flushing it thru? Also, while off, try undoing the two valves, one a time (very slightly cos you dont want to flood the room!) to see if they are opening properly.
you say you flushed it. Did you use a cleaning chemical? when you refilled it, did you use a corrosion inhibitor?
Has your system got a feed and expansion tank in the loft, and did you scoop the mud out and sponge it clean?
Have you got thermostatic radiator valves?
If you turn off all the other radiators, does this one get hot?
Has your system got a feed and expansion tank in the loft, and did you scoop the mud out and sponge it clean?
Have you got thermostatic radiator valves?
If you turn off all the other radiators, does this one get hot?
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@WabbitPoo
The valves are brandnew on either end due to the new rad. The rad itself is new so no sediment. We have just tried to bleed the radiator again with the lockshield turned of and the wheelhead valve pipe became hot but as soon as we turned of the bleed and reopened the lockshield it went back to cool again straight away.
@John
We only flushed the old rad. not the whole system. Didn't use any chemicals. We only have a trv on the bathroom rad and that one seems fine although only heats when turned to 4 or 5.
Turning the other rads of is a problem due to the age of the rads they are very stiff and immovable.
The valves are brandnew on either end due to the new rad. The rad itself is new so no sediment. We have just tried to bleed the radiator again with the lockshield turned of and the wheelhead valve pipe became hot but as soon as we turned of the bleed and reopened the lockshield it went back to cool again straight away.
@John
We only flushed the old rad. not the whole system. Didn't use any chemicals. We only have a trv on the bathroom rad and that one seems fine although only heats when turned to 4 or 5.
Turning the other rads of is a problem due to the age of the rads they are very stiff and immovable.
in that case you will not have been able to balance the system. that will be one reason for your radiator not heating up.
As you did not use a cleaning chemical or inhibitor we can expect your system to be clogged up with corrosion sediment and sludge. Some of this sediment is hard, and some of it will flow around the system and settle in your new rad.
If you have got a feed and expansion tank in the loft (you did not answer that one) tie up the ball valve and bale out the mud and water, and sponge it clean. Buy a litre of Sentinel X400 at your DIY shed or plumbing merchant for about £15 (it is non-aggressive and easy for DIY use, do not buy a substitute), tip it into the F&E before you refill it, and drain a bucketful of water out of the drain cock. When you untie the ball valve and stir in the Sentinel, it will be drawn down into the radiators to replace the bucket of water you drained out.
When the circulating water goes jet black, you will know the X400 is loosening the old black sludge.
After 4 weeks drain it out and rinse the system. On final flush add a litre of Sentinel X100 to prevent future corrosion.
Most often this will loosen and wash out enough sludge to get the system working again. Powerflushing costs hundreds of pounds and is the next step if you can't get it clean with the chemicals.
While you have it drained you might think about replacing those old jammed valves with new ones. Rad valves only cost a few pounds each. If the pipes run along the walls or come out of wooden floors, they will probably have enough slack on them to fit replacements. However if they are held firm in concrete floors it is much more difficult.
Do the chemical clean first. You can start today.
M
Morris40
just a point to make, you said your pipe is 8mm this is microbore pipe and powerflushing is VERY ineffective on this type of system.
It seems that you realise the poor condition of your system and that its full of dirt.
I would recommend draining, replacing all the old valves and then filling and adding X800 and leave that circulating for just one day.
X800 is stronger and quicker than X400.
Tony Glazier
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Whilst he does often admit that he is not a professional, thats not the best advice.
As I said the start should be to replace the old rad valves. Until thats done the system cannot be properly balanced.
A microbore system is largely self balancing though.
Tony
As I said the start should be to replace the old rad valves. Until thats done the system cannot be properly balanced.
A microbore system is largely self balancing though.
Tony
My thinking was that (if they have an open-vented system) they could tip it in quickly and easily with no drain down or taking things apart, and it would make a good start to get on with the cleaning.
Draining down and taking all the valves off needs preparation and means you are without heating until you've finished, so is a job that would be put off until tomorrow, or the day after, or the day after that...
I like things to be clean
Draining down and taking all the valves off needs preparation and means you are without heating until you've finished, so is a job that would be put off until tomorrow, or the day after, or the day after that...
I like things to be clean
Its no use just flushing your one rad, as can be seen from these other posts.
Is it a combi boiler? If so, is there much pressure in it?
Just swap the wheel head with the LS cover; they have been put on the wrong way round! Radiators are bidirectional.
Was the boiler on when you did this? Bleeding should always be done with the boiler off and the water cold.
@JohnD
Many thanks for the reply. I read on posts to other questions that balancing you only change the lockshield side until 11degree difference so wasn't sure about having to change the wheelhead side which is why we thought we had balanced it. If there was a problem with the balancing would it have worked correctly for the first month we put the new rad in?
With regard to the feed expansion tank we have no loft ladder, flooring up there or the guts to tiptoe about. The last time we had a plumber up there he said there was no cover on the tank so this could be letting dirt into the tank.
As I can't get up there would draining the system, letting it refill and draining it again maybe do the trick or do you think there could be a blockage which is somehow letting cold water past the wheel head but not hot? Water pressure on the wheelhead side does seem diminished.
I like the idea of changing all the valves at this time though.
@Morris40 Thanks for that info: at £300 per pop that was our last resort.
@TonyG Thanks for the reply. Would the x800 need to be added to the FE tank also. I have read of products that can be put into the bleed valve on the first rad in the link. Would this work to save falling through the ceiling?
@WabbitPoo It is a combi boiler Glow.worm Micron 50FF with a hot water tank underneath. As I said it is always this 1 rad that had been the problem over the last 2 years but in the 5 previous years it was fine so I'm hoping it is a sludge problem, rather than a boiler problem.
@D_Hailsham Would that it were as simple as that but if that were the case when both side were open fully then the rad should heat up and that doesn't happen. From previous unrelated threads I can see that rads can be bidirectional but from my understanding the heat from the lockshield side it redisdual heat left in the water after passing through the rad on its way back to the boiler to be reheated which is why although my rad is heating on the lockshield side it isn't really giving heat to the room only heating the rad. Also if it were a matter of just changing the caps on top that wouldn't change that the rad was working fine for 1 month after refitting it. The boiler was on when we blead as when it wasn't there was no water pressure to push the water through and I wanted to see if there was a flow from the lockshield side.
Many thanks to all. I think next week we will drain and change the valves. I'll keep you posted.
Many thanks for the reply. I read on posts to other questions that balancing you only change the lockshield side until 11degree difference so wasn't sure about having to change the wheelhead side which is why we thought we had balanced it. If there was a problem with the balancing would it have worked correctly for the first month we put the new rad in?
With regard to the feed expansion tank we have no loft ladder, flooring up there or the guts to tiptoe about. The last time we had a plumber up there he said there was no cover on the tank so this could be letting dirt into the tank.
As I can't get up there would draining the system, letting it refill and draining it again maybe do the trick or do you think there could be a blockage which is somehow letting cold water past the wheel head but not hot? Water pressure on the wheelhead side does seem diminished.
I like the idea of changing all the valves at this time though.
@Morris40 Thanks for that info: at £300 per pop that was our last resort.
@TonyG Thanks for the reply. Would the x800 need to be added to the FE tank also. I have read of products that can be put into the bleed valve on the first rad in the link. Would this work to save falling through the ceiling?
@WabbitPoo It is a combi boiler Glow.worm Micron 50FF with a hot water tank underneath. As I said it is always this 1 rad that had been the problem over the last 2 years but in the 5 previous years it was fine so I'm hoping it is a sludge problem, rather than a boiler problem.
@D_Hailsham Would that it were as simple as that but if that were the case when both side were open fully then the rad should heat up and that doesn't happen. From previous unrelated threads I can see that rads can be bidirectional but from my understanding the heat from the lockshield side it redisdual heat left in the water after passing through the rad on its way back to the boiler to be reheated which is why although my rad is heating on the lockshield side it isn't really giving heat to the room only heating the rad. Also if it were a matter of just changing the caps on top that wouldn't change that the rad was working fine for 1 month after refitting it. The boiler was on when we blead as when it wasn't there was no water pressure to push the water through and I wanted to see if there was a flow from the lockshield side.
Many thanks to all. I think next week we will drain and change the valves. I'll keep you posted.
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