Pure water equipment, which uses mainly reverse osmosis membrane technology. Its working principle is to exert a certain pressure on the water, so that the water molecules and ionic mineral elements through the reverse osmosis membrane, and most of the inorganic salts dissolved in the water (including heavy metals), organic matter and bacteria, viruses, etc., can not pass through the reverse osmosis membrane, so that the penetrated pure water and the concentrated water can not be strictly separated; The aperture on the reverse osmosis membrane is only 0.0001 micron, while the diameter of viruses is generally 0.02 to 0.4 microns, and the diameter of ordinary bacteria is 0.4 to 1 micron.