Japanese tap water is transparent and cleanly treated. However, this clear water contains ions such as sodium, calcium, and chlorine, as well as silica. Therefore, a removal may be necessary for an use as manufacturing water. These ions cannot be removed by physical filtration using filter sand or anthracite. An ion exchange resin tower is a device that removes unwanted ions from water by exchanging the ions held by the resin with the ions in the water that need to be removed.