I don't know if anyone else has been watching the "conductivity: levels at the Barrage since they opened the sluices last Sunday?
The higher the conductivity figure the more "crap, silt, metals, sulphates, etc. there is in the water.
To run a High Pressure Boiler you need to take out all the crap mentioned above and use virtually distilled water with a conductivity of 1 - 3. To attain this they put water though a demin plant.

OK now the lesson is over, the "normal" condutivity at the Barrage is anywhere from 60 - 80 odd. That means there is a lot of "foreign matter " in the water.
Since they increased the flows and opened the Vaal Dam sluices the conductivity has dropped from 60odd to 34 to 29 today.

That's good news indeed, ito cleaning the whole system, all the way to the Orange.