"It is not as quick as the acid cleaners, but is much easier and safer to use. I have had damage to skin and clothes from spillages of acids, and you have to rinse and flush them out very thoroughly.
X200 is mild and seems harmless, and you don't have to drain it out or rinse it - you leave it circulating in the system permanently.
It works faster if you add it in summer when the radiators are all turned off, then it is more concentrated in the boiler HEX and hot-water system because it does not mix with all the water in the radiators.
It may take a month or two to achieve its best
You may need two bottles if the system is very large or scaly."
"I found this very easy to add into the heating system - Drain an amount of water from the system whilst isolating the header tank then add to the header tank and refill the system. So far it appears to be working well."