Before this, during the early development of the Japanese tea ceremony, corners of large reception rooms were partitioned off for tea-making, and there was no specific area or space designed for the preparations.
The most modest modern mizuya may comprise little more than a hot-plate or electric kettle and several buckets of fresh water, and might be located in a screened-off outdoor area with a grass floor.
A fully equipped modern indoor mizuya may rival the best-equipped kitchen, with several sinks with hot and cold running water, an elaborate system of storage areas, cupboards, shelves and worktops, a refrigerator, stove, and microwave oven.
A typical indoor mizuya has in it a recess three or four feet wide and two feet deep, the mizuyanagashi, possibly with a tatami mat in front of it, equipped with a traditional sink, the nagashi (a long metal tub sunk into the floor and covered with a bamboo grate called sunoko), several wooden shelves for storing tea supplies, and a board with pegs for hanging ladles and towels.
It is built into the wall of the tea room, at floor level, on the side where the host's mat is situated, and has sliding doors so that it can be closed from view of the guests.