Hard water and water heater leaks
The City of Anaheim puts its water hardness at about 300 parts per million, or roughly 18 grains per gallon. In the city's words, "Hard water leaves mineral deposits on pipes, appliances and dishes." Inside a water heater, those minerals settle as sediment at the bottom of the tank. A guide from the U.S. Department of Energy's Building America program notes that this buildup reduces how well the heater transfers heat, and recommends flushing the tank.
When a tank finally leaks, the water spreads across the garage or closet floor and into the walls around it. Water heater leak cleanup in Anaheim starts with closing the cold water valve on top of the tank. California law also requires water heaters to be strapped against earthquakes, so check the straps when the heater is replaced.