Limescale Buildup
This couple noticed that from time to time, the showerhead in their shower was covered with white spots. They isolated it with a plastic bag in order to see what happens, and after a week, they discovered this strange, white powder accumulated in the bag and outside of it. They assumed it was something added to the water.
As one Reddit user pointed out, this was probably limescale buildup. Limescale is a solid, chalky deposit that often builds up inside kettles, hot water boilers, and pipework – so it makes sense they found in on their showerhead. This might indicate the pipes are old and needs to be replaced, but there are easier solution. Either way, while limescale isn’t dangerous, it’s better to treat the problem and eliminate it.