At present, Oman faces a serious problem on water shortage due to lack of freshwater sources and low underground water levels. Conversely, Oman has a high level of solar radiation and various types of rocks. Three different types of local rocks have been used in this study, namely, basalt rocks, concrete bricks and crashed rocks, to enhance the productivity of water by increasing the time of output from the double-slope solar still. Results revealed a remarkable increase in the productivity of the basin with concrete bricks by 42%, which was more than that of the productivity of the basin without concrete at 7 pm. Moreover, the productivity of the basin with igneous rocks was improved by 111%, which was more than that of a clear basin at 7 pm. The maximum water temperature of the basin with concrete bricks and the clear basin was 73.2 °C and 75.2 °C at 1 pm, respectively. In addition, the maximum water temperature of the basin with igneous rocks and the clear basin was 71.6 °C at 3 pm and 77.3 °C at 2 pm, respectively.