Earth's current lack of clean water has necessitated a search for new water sources; desalination of the sea water has been regarded as the best solution. Many techniques have been developed to make sea water into drinking and utility water. Recently, clean water production by the condensation of evaporated salt water at low pressure is one of the commonly applied techniques. Low pressure is obtained by a natural vacuum and renewable energy using a vacuum pump. In the study, system efficiency was examined for desalination at low pressure formed by vacuum pump at 0, -15 or -25 C-omicron condensation temperatures. The volume of desalinated water was measured for each evaporation temperature at 45, 50, 55 and 60 C-omicron, and the efficiency for a given volume of desalinated water at decreased temperatures at condensation temperatures below 0 C-omicron. In each experimental group, salt water could be purified by an average of 99.6%. However, according to the data obtained at 0, -15 or -25 C-omicron condensation temperatures, it was determined that decreasing the condensation temperature to -25 C-omicron was redundant: a similar efficiency could be obtained using less condensation energy at 0 C-omicron. (C) 2017 Elsevier B.V. All rights reserved.