Kettling noise in boiler - micro-leaks in water pipes

[davidbradbury]

Hi. Not an unusual post I see, but I've done most things I can think of. I spent about £700 this year having a plumber replace a pipe from my boiler to the tank and flush the system completely to eliminate boiler noise I was getting. This worked for about two days after I switched on the heating again this winter and I'm reluctant to hand over large sums again to achieve nothing. The boiler is only two years old.

Could the air in the system be due to micro-leaks in the pipes? sometimes I can bleed a radiator of air for five minutes or so, sometimes I don't have to bother for a week - either way the kettling in the boiler remains, whether the radiators are fully bled or not. It kettles away only while the boiler is actually heating water. Does anyone know of a tool or method to try and locate air leaks? Or is this not a practical idea or reasonable assumption about what is causing the kettling?

Thanks
David

 

[ChrisR]

YOu don't need air for kettling. Scale in the boiler means that the water under the scale can boil locally. The bubbles make the noise. Do you know what chemical yer man used when flushing (if any)? You could try Sentinel X200 boiler descaler or Fernox Boiler silencer. If I rem cor you can leave either of them in the system.

The above may get dissolved air out, but that should stop after a bit.

Are you sure there's corrosion inhibitor in the system?? Collect some of the gas and see if it's hydrogen from corrosion. (upturned jar, to hold it, introduce match & hear the pop)

 

[ChrisR]

YOu don't need air for kettling. Scale in the boiler means that the water under the scale can boil locally. The bubbles make the noise. Do you know what chemical yer man used when flushing (if any)? You could try Sentinel X200 boiler descaler or Fernox Boiler silencer. If I rem cor you can leave either of them in the system.

The above may get dissolved air out, but that should stop after a bit.

Are you sure there's corrosion inhibitor in the system?? Collect some of the gas and see if it's hydrogen from corrosion. (upturned jar, to hold it, introduce match & hear the pop)

 

[oilman]

How did he do the flushing?

 

[davidbradbury]

I'll try collecting some gas to see if it's a corrosion issue.
The plumber I had used some enormous machine to do the flushing, and according to his bill he did a "Power flush, refilled the system, added inhibitor and tested".

 

[oilman]

I think from this, the problem is likely to be a badly scaled boiler. The problem with power flushing is that it can't return a system to new, it will always be an old system. The boiler gets scsled from years of neglect, and then we get fed information that the problems can be cured overnight. You may benefit from adding some boiler noise reducing chemical, though it would have been better added before the inhibitor.

The way to descale the boiler is to disconnect it from the system and do it as a seperate unit. You could hire a descaling pump, and it will take all day.

 

[davidbradbury]

Thanks for all your advice. I'll investigate the descaling option.