An apparatus and method for manufacturing deionized water is provided. Water is supplied to a first conduit. A plurality of reverse osmotic pressure vessels are connected to the first conduit. A filtering experimental vessel is connected to the first conduit, the filtering experimental vessel is separated from the plurality of reverse osmotic pressure vessels. A second conduit is connected to the plurality of reverse osmotic pressure vessels and the filtering experimental vessel for outputting the deionized water. A third conduit is connected to the plurality of reverse osmotic pressure vessels and the filtering experimental vessel for outputting concentrated ion water. The plurality of reverse osmotic pressure vessels and the filtering experimental vessel concurrently or independently separates the supplying water into the deionized water and the concentrated ion water.