Water onboard comes from 3 sources:    Water produced onboard from a flash evaporator (the most common and largest producers), produce distilled water with a sodium content below 10ppm (the alarm limit, where the water produced is dumped overboard if above this limit), but more commonly around 0-1ppm.   Water produced onboard from a reverse osmosis water plant, which produces water with a sodium content below 20ppm (again, the alarm limit where the water produced is dumped),