A twin electrodialyzer with a common anode, in which first an ED stack was packed with non-conducting spacers and second an ED stack was packed with ion-conducting spacers, was developed and tested under various experimental conditions. Experiments were conducted on a laboratory scale at different voltage and flow rates. Each membrane had an effective area of 65 cm. Two configurations of the twin electrodialyzer [configuration (1), ED stack 1:7 cell pairs and ED stack 2: 7 cell pairs; configuration (2), ED stack 1: 10 cell pairs and ED stack 2: 7 cell pairs] were optimized for the production of demineralized water. The results show that from inlet NaCl solutions of 500 and 800 ppm concentrations with conductivity 0.75 and 1.26 mS cm(-1), respectively, with a linear velocity 2.52 x 10(-3) in s(-1) and at applied voltage 1.5 to 2.0 V/cell pair, an outlet conductivity ranging between 15.0 to 20.0 muS cm(-1) was obtained using a twin electrodialyzer. It was concluded that with the twin electrodialyzer, both the stacks perform in an efficient manner, and it is possible to achieve a high degree of demineralization at a lower flow rate and low electrolyte concentration.