Another name for this is ground water. Residents on the west side of the river drink water from Seattle's Tolt Reservoir, over 20 miles away in the Cascade Mountains east of Duvall. Hardness in water comes from minerals like calcium and magnesium. Soft water is easy to make lather with soap. Sometimes my water tastes good and other times it doesn't.
Water is the universal solvent.
When it sits in pipes over night or for a few days it will warm to room temperature. The chlorine will have had a long time to react to the insides of your pipes. The water will taste musty, stale or like medicine. To improve your water quality, flush your cold water tap until it starts to get colder, usually about 1 minute. Now you have fresh cold water from the water main.