Barnstead E-pure Water Purification Systems Barnstead. This system utilizes molecular sieves and molecular filtration for the removal of ions that can not be dissolved in water. Ideal for applications requiring very clean water the system utilizes hollow fiber membrane technology. The actual number of molecular sieves and filtration steps depend on the type of water and the degree of contamination of the source water. Operating parameters of the E-Pure Water Purification System are set automatically to correspond with the purified water quality data from your laboratory. Barnstead E-pure Water Purification Systems Barnstead D5023