On this forum I was laughed at by other installers because I use X300 to flush a new radiator system. Seems no one else on here ever does!
One of the worst systems that I ever went to was only seven weeks old and the pump had been spoilt by dirt caused by untreated flux having dissolved the steel on the inside of the rads.
Tony
Only time I ever fitted a full system from scratch I used X300, hot flush, then multiple cold flushes till water was colourless, 3 years on I took a sample and it looked like drinking water it was spotless. I sometimes wander if the "Sludge" removal chemicals are that good with flux
Seriously SGM, you've only ever fitted one complete system in your whole career?? Frankly I'm amazed by that!!!