I recall reading a report from the Santa Fe dating from the late teens-early twenties concerning locomotives that were based in Winslow, AZ. Water conditions were so bad there that boilers were washed after every trip. If there was no time to wash the boiler, it was drained and refilled with fresh water. Boiler tubes were routinely replaced annually, and fireboxes renewed every five years.
They kept a LOT of people employed in Winslow keeping trains moving.
Water treatment was a lifesaver for the Santa Fe.