As part of my nightmare of coolant system, I have ended with the water pipes from the barrel removed, repainted, and now coming back to place, but realised that a lot of limescale (mixed with the rust of the old metal pipes of my bike) has behind left on the wall of the barrel.


You can see the level of limescale on here:



Does anybody know of a good way of removing it?


Should it be good to go with new O-ring a proper greased? (I am thinking going this way, to avoid doing more bad than good, and in the hope that it will not end worst than it was before I started the works... And I can always remove it again and put new O-rings again...


Thanks a lot in advance,