The parameters of the water transport model from a wet cloth sheet to the air, developed for the de-ionized water to establish design procedures of the onsite volume reduction system, were identified for high salts concentrations present in the synthetic urine. The results showed that the water penetration was neither affected by the salts, the urea and the creatinine present in the synthetic urine nor the salts accumulated on the surface of the vertical gauze sheet. However, the saturated vapour pressure decreased leading to reduction in the evaporation rate, which occurred due to the salts accumulated on the surface of the vertical gauze sheet. Furthermore, the steady-state evaporation condition was established illustrating salts falling back to the tank from the vertical gauze sheet. Accordingly, the existing design procedure was amended by incorporating the calculation procedure for the saturated vapour pressure using Raoult's Law. Subsequently, the effective evaporation area of the vertical gauze sheet was estimated using the amended deign procedures to assess feasibility. This estimation revealed that the arid, the tropical, the temperate and the cold climates are suitable.