A Practical Manual On Sea Water Distillation
With A Description Of The Necessary Machinery For The Process

8 SEA WATER DISTILLATION. Evaporator Feed Pump. 3. A force pump is sometimes also required to feed the evaporator—that is, when it works under pressure— otherwise the evaporator feed may be allowed to gravi- tate into the evaporator without the need of forcing it in by means of a special pump. The fresh-water pump usually takes the water from the filter and forces it into the drinking water tanks,, but this distilled water can be diverted from the filter, and be run or pumped elsewhere to add to the boiler feed-water if desired. Gained Steam—Discharge of. 4. At one time it was customary for the evaporator on board to discharge its gained steam—that is, the steam or vapour it has generated from sea water—direct into the surface condenser on board, instead of into the dis- tilling condenser as above described. This, as will be shown hereafter, requires more or less special appliances, as the surface condenser is worked under atmospheric pressure more or less variable, whereas the distilling con- denser ordinarily works at atmospheric pressure. Fixing above and below Water Line. 5. From the above summary description of a double distiller as used on steam ships, it will be seen that a rather different system of working may be adopted, according as the apparatus is placed either above the sea water line—that is to say, placed on an upper deck—or is placed below the sea water line, say in the engine-room. 6. In the first case the fresh water, as it is produced, can flow into a tank alongside of, or just below, the apparatus, and then pipes may be laid for the fresh water