A vertical dip pretreatment and electro-deposition system has a plurality of dip stations and a plurality of spray stations. The process limited dip stations, such as the degrease dip station, the phosphate dip station and the electro-coat dip station, have expandable dip tanks which can have a bulkheads that divide the tanks into two sections providing the tanks with two compartments, or have removable end walls that can be removed and replaced with a tank section. If the bulkhead divided tanks are used, during the initial period of operation when production rates would typically be less than ten to twelve jobs an hour, one compartment of each expandable dip tank is used for immersion and the other compartment left dry or used for other purposes such as storage. When volume increases to above the design capacity, the expandable tanks are expanded. If bulkhead divided tanks are used, the bulkhead is removed which joins the first and second compartments, thus doubling the length of the tank. If the removable end wall tanks are used, the removable end walls are removed and replaced with tank sections to double the length of the tanks. In operation, the system is then set up so that after the product is lowered in the expanded tank, it stays in the first half of the expanded tank for half or less of the process time. The product is then kept in the lowered position in the expanded tank and moved to the second section of the expanded tank where it remains until the end of the required process time. The index time for the system is thus half or less of the total cycle time of the process. In this manner, production throughput of the system is increased.