Lots of people in warm climates use plain water in their washer tanks. Saves a little money. Then again I've seen people forget to add the chemicals and the tank freezes up. Sometimes ruptures. Used to be A common practice in Florida for people to use plain water all year but to run out before a hard freeze and add a little alcohol to the tank.

Not mentioned in the article there is some thought that the evaporator can support legionella bacteria if the drain is plugged. Fact being that most cases of legionnaire's disease have been associated with evaporator drain pans and cooling sprays on buildings. the thought is that similar conditions could be present in the AC system of a car if the drain isn't clear. Nothing like stagnant fresh water kept warm to breed critters.