Unevaporated water flows through an orifice-which maintains pressure different into the second chamber where more water is evaporated since the pressure is than in the first chamber. brine pump extracts low-density unevaporated water and discharges the bu side of the supply pump the bulk overboard. Some however may return to the suction the auto-valve B to maintain the feed inlet temperature at about 30°C irrespective. how low the sea water temperature may be.