In this paper, an attempt has been made to investigate the impact of salt concentration on the internal heat transfer coefficients of a geographically south facing conventional solar still. The experiments were conducted on seven different days for seven different salt concentrations (i.e. 0%, 0.5%, 1%, 1.5%, 2%, 2.5% and 3%). The evaporative heat transfer coefficient at 1% of salt concentration is higher by 461.70%, 82.63%, 144.95%, 71.54%, 146.91% and 156.12% as compared with the 0%, 0.5%, 1.5%, 2%, 2.5% and 3% of salt concentrations, respectively. An average value of overall heat transfer coefficient at 1% of salt concentration has maintained its lead throughout the experimentation as compared to other salt concentrations. On the basis of results obtained through the experimental and theoretical evaluation, it has been observed that at 1% of salt concentration the distiller unit will give better performance. © 2019 Informa UK Limited, trading as Taylor & Francis Group.