i have worked on the dawn princess

They get most of their water from shoreside as demand outstrips what they can make. They have three flash evaporators 2 big and one little running off waste heat from the engines. from there it went forward to the water tanks and on they way it was stuffed full of chlorine and then taken from the tanks and pumped to the hotel services. And on its way it is decholiriated with i think it was sliver iodide or something similar but iwas pain in the arse system to get right.

but in the end it should be about 0.2 ppm or 2ppm can't remeber at your taps