The effect of water film cooling of the glass cover on the efficiency of a single basin still is theoretically investigated. The effectiveness of film cooling under different operating conditions is reported. Part of the cooling water is recycled as makeup water to the still to further enhance its efficiency. The results of this investigation indicate that proper use of film cooling parameters can increase the still efficiency by as much as 6 percent, but poor combinations of film cooling parameters can lead to significant reductions in still efficiency. The presence of the cooling film neutralized the effect of wind speed on the still efficiency. The actual gain in still efficiency due to the use of a cooling film is further amplified when the practical considerations of where and how such a still is used are taken into account.