NOVELTY - A water separating system comprises water electrolysis, hydrogen-oxygen recombination and rectifying system having one-level or multi-level structure. Each level of the structure comprises a water storage tank, rectifying tower, gas-liquid separator, heat exchanger, electrolysis-recombiner, one-way valve, switch valve, computer control center, electrolysis power supply, residual heat power generator, water pump, steam pump and a connecting pipeline.    USE - Water separating system useful for separating deuterium-containing water from protium-containing water in purified water.    ADVANTAGE - The water separating system can effectively separated the water-containing protium from the purified water, where content of separated deuterated water is reduced from 150 ppm to less than 100 ppm.    DETAILED DESCRIPTION - A water separating system comprises water electrolysis, hydrogen-oxygen recombination and rectifying system having one-level or multi-level structure. Each level of the structure comprises a water storage tank, rectifying tower, gas-liquid separator, heat exchanger, electrolysis-recombiner, one-way valve, switch valve, computer control center, electrolysis power supply, residual heat power generator, water pump, steam pump and a connecting pipeline. During the operation process of the system, the water pump is for injecting deionized water into the electrolysis recombiner for electrolysis and synthesizing the generated hydrogen with oxygen to produce the water with low deuterium content, which is the ultra-light water. The oxygen produced in the electrolysis and the residual water is feed into the rectifying tower. The upper and lower parts of the rectifying tower are at different temperatures. The solid and/or liquid catalyst is placed in the tower. The protium water and the deuterium water can be exchanged. The rectifying tower is made of ceramic, stainless steel or plastic. After the materials are exchanged in the rectifying tower, part of the water is discharged from the top together with the oxygen in the form of liquid and/or gas, then fed into the gas-liquid separator through the heat exchanger. The gas-liquid separator is used for separating gas from liquid. The separated water and oxygen are fed into the electrolysis-recombiner. The residual heat obtained after the heat exchange is fed to a residual heat power generator to generate power. The other part of water with high deuterium content is discharged from the lower part of the rectifying tower, and the low deuterium water can be separated from the high deuterium water. An INDEPENDENT CLAIM is included for a depleted deuterium water produced for brewing wine, where content of deuterium oxide of wine is lower than 140 ppm.