In this paper, comparison between theoretical and experimental anaylis of an open type flat collector for tannery effluent treatment is presented. Effect of the parameters like insolation, wind speed, relative humidity, mass flow rate and salt concentration on the evaporation rate of water in the effluent is studied. An open type fibre reinforced plastic (FRP) flat plate solar collector is used for experimentation. The evaporation rate increases for increase in insolation, wind speed and mass flow rate and decrease in relative humidity and concentration. © 2003 Elsevier Science Ltd.