Why does the UK have separate hot and cold taps?
While mixer taps are fairly common, separate hot and cold taps are still prevalent in UK bathrooms. The reason for this is an historical one, as hot water was often stored in a cistern or cylinder in the home, whereas cold water came from the mains supply. The cistern-stored hot water was not safe to drink, while the cold water was. Differences in water pressure could also affect the stream of water out of a mixer tap.