It's happened before
Tucson is situated over a gigantic underground lake--something reinforced when the town began subsiding, bit by bit, and sinkholes became an occasional problem. As one would imagine, excess removal of water from the lake caused the issue.
To mitigate this, water was brought in via canals from Phoenix, known as CAP (Central Arizona Project) water.
Initially, the idea was to use a blend of CAP and underground water. Tucson water was, previously, not soft, but pretty tasty, from the nice balance of minerals in the lake. It was alkaline, and coated the galvanized pipes prevalent in the area with a nice layer of calcified buildup, which helped protect the pipes from being directly exposed to the water.
Once Tucson Water switched to CAP water to alleviate the demand on the lake, all heck broke loose; this water was acidic, and it ate away the minerals in the pipes--and the pipes themselves. Leaks sprang up all over the city, and many homes had to be completely replumbed. Property damage from mystery leaks was rampant; you probably would prefer to turn off water at the meter if you were going away for the weekend.
Eventually, Tucson Water dialed the blend of CAP water way back, and started diverting a large portion of the CAP allocation to giant recharge pools to the west of town, hoping that the water would be conditioned by percolating through the soil, and re-enter the underground aquifer. The issues subsided, and the water's still pretty nice--but it's anyone's guess as to how long it will take for the recharge water to have a great effect on the lake's levels. Other changes that coincided--like xeriscaping, and eschewing large, lush lawns helped reduce water demand, too. (Golf courses and other water-hogs started using reclaimed water, instead of drinking water, to tend to the grass.)
At the time the chaos was going on, your tap water looked exactly like that Amana above. Yuck. Were it an event in the hyperconnected Internet era, rather than the early 90s, it might have made more of a ruffle.
Switching water supplies is never a trivial issue--unless you're lucky enough to have nearly identical chemistry, which seems to pan out just shy of never.