The objective of this investigation is to study the influence of application of phase change material (PCM) in solar basin stills for improving its productivity. The experimental results of this investigation showed that using phase change material (paraffin wax) in solar basin still improved its daily productivity, which increased with increasing the mass of phase change material. The highest increase ratio of daily productivity was 26.3[%] when using 3.5[kg] of phase change material in plastic case, and it was 34.74[%] when using 4.5[kg] of phase change material (PCM) in metal case. Also the experimental results of this investigation showed an increase in the period of working basin still provided with phase change material compared with basin still without phase change material. This is owing to the latent heat stored in phase change material, which is emitted to water when solar radiation decreases. This results in longer period of work for the basin still.