DH I am aware of what you say BUT a cleanser will remove the sediment so heat transfer not diminished. dS40 and ferroquest come to mind which I have used effectively in the past
Anyhow, if I was intending replacing th boiler some time in the future, I would clean the present system and get it ready for transfer later
Anyhow, if I was intending replacing th boiler some time in the future, I would clean the present system and get it ready for transfer later