This work presents a numerical simulation of capillary film solar still (distiller) coupled in series with another conventional solar still. Different transfer phenomena of heat and mass are considered to evaluate the daily distillate production. The study takes into account the quality of brackish water with moderate salinity in Adrar city (south of Algeria). The performance of the system is evaluated and compared with that of conventional solar still under the same meteorological conditions. A numerical simulation is carried out to appreciate the developed model and to optimize the relationship between both distillers collecting surfaces. The obtained results show that the system daily production is at 54-83% higher than that of the conventional one. In addition, some parameters influences are studied to define the optimal operating conditions for the present system. For the first solar still, the inclination angle and surfaces ratio have a significant effect on distillate production. Brine flow rate and wind speed have slight effect on still production. (c) 2014 Elsevier Ltd. All rights reserved.