Capacitive Deionization (CDI) is an emerging technology for brackish water desalination. So far, very promising electrode materials with excellent performance have been only tested on a small scale, mainly, because of scalability issues. With the desire of finding a stable and easy to scale electrode from an engineering point of view, advances from the energy storage field have been implemented here. In this fashion, 3D composites were prepared using the highly conductive macrostructure of a graphite felt (GF) as electron transfer channel and the microstructure of activated carbon (AC) to furnish ionic adsorption sites (GF-AC). The electrochemical characterization of the 3D composite at small scale showed a larger total ion storage capacity as compared to an AC film electrode prepared with the same active material. Moreover, the composite also shows a great stability that the specific capacitance retention is high after 5000 charge/discharge cycles. The 3D composite was was then tested in a 1-Cell CDI System (10 cm²) reaching high salt adsorption capacity (SAC) values and charge efficiency. Subsequently, long-term operation testing resulted only in a 30% SAC capacity loss after more than 100 cycles. Finally, the system was scaled to a 9-Cell Stack (300 cm² electrodes) and was able to demonstrate excellent CDI performance. In general, the 3D electrodes provide several advantages for capacitive deionization, including a well-dispersed amount of active material with high mass loading, a simple preparation, easy scalability and good cycling stability. Therefore, we believe that GF-AC electrodes hold promise for large-scale CDI practical applications.