I had new glow worm 30cxi installed 2 yrs ago, serviced every year since. The pump is making nasty noises, engineer drained some water for testing and it was the colour of guiness. He says the system wasnt flushed on install. Installation book says X300 flush and X100 inhibitor have been used, but that is for new systems. Mine used all the old rads and most of the existing pipework. I'm now being quoted for a powerflush, magnate (sp?) crap remover and probably a new pump. Any advice please? Should I be giving the installers grief?