I would appear that we over a period of 5 years have developed a build-up of lime-scale on our black/grey tank walls. This is now breaking up in smaller and larger chunks, and our macerator system is not too happy with this. It looks like thick plastic flakes - smooth on the side where it was stuck to the tank walls, and rough on the other side.
If this was my water heater I would not hesitate in treating the problem with something like a vinegar solution, but two large tanks is probably a different kind of problem. My immediate thought is to "bombard" the tanks with something like Calgon water softner, or even a large helping of Calgon dishwasher tablets, but whether this is too aggressive I am not sure. I don't want to solve one problem and get 5 other ones.
What do you think is my best bet to get rid of the lime scale, preferably in one hit, apart from applying a stick of dynamite