HCDHCa hard white or grey substance that forms on the inside of pipes, taps, and water containers 水垢
Examples from the Corpus
limescale• The main enemy of these pumps is limescale, so consider a magnetic device on the feed into your pump.• There was a lot of limescale on the bath.• This unit removes calcium and magnesium from the water, preventing limescale from building up in the machine and on your tableware.• I just scrub and scrub, I've got all the limescale off the bath.