For something that is pretty formless, it’s hard to wrap your mind around water being “hard.” Believe it or not, groundwater contains metals, causing it to become hard. Hard water can contain high quantities of calcium, magnesium, or other minerals by absorbing them from soil and rocks.

While this sounds like something that may be potentially unsafe, hard water is more dangerous for your plumbing than it is for your consumption. Minerals collected by water can show up in your pipes, water heaters, and dishwashers as “scale.”