City and town water works, asylums and hospitals, plantations, railway water tanks, irrigation, private country houses, pumping mines, ice manufactories, breweries, cold storage and packing houses, textile mills, dye works, bleacheries, sewerage installations, dry docks, seaside water works, stock farms; in fact, everywhere that clear and abundant water is needed are opportunities for the application of the Air Lift System of pumping water.
Nor is it alone for securing public water supplies that the Air Lift is of special value. Within recent years the question of an abundant and pure water supply for manufacturing, irrigation and other uses has become one of equal importance. After an extensive experience, two general systems have been devised for utilizing the water which lies immediately below the surface of the ground. One, known as the Deep-well Pump System, for which a working pump is used, and the other the Air Lift System, which employs compressed air to raise the water, either by means of its inherent expansive force or the difference in specific gravity between compressed air and water.
Note.—Dr. Julius J. Pohle is admitted to be the original inventor of this admirable and useful device. At first all systems by which water or liquids were lifted by compressed air were more or less extravagant, but with large experience and with improvements in air compressor economy, the Air Lift has made valuable strides. Dr. Pohle was actively associated with the Ingersoll Sargeant Co. until his death, 1896, since which time his system has been further improved and developed by a wider application and broader experience.
Theory of the Air Lift. Opinions differ as to the true theory of the Air Lift. A common Air Lift case is one where there is a driven well in which the water has risen approximately near the surface. In this well is placed a large pipe for the discharge of the water, which is known as an “eduction pipe.”
Fig. 378.
This pipe does not touch the bottom of the well, but is elevated above it so as to freely admit the water through its lower open end. Alongside of this pipe, either on the outside or within, is a small pipe properly proportioned and intended to convey compressed air to a point near the bottom of the eduction pipe. It is usual to provide a “foot-piece,” see Fig. [378], which forms a nozzle connecting the air pipe with the water pipe, but in what is known as the “central pipe system” this foot-piece is not used, the air pipe being placed within the eduction-pipe to a point near the bottom, where it discharges the compressed air into the water column.
Many neighborhoods are dependent upon well water, and there are few districts where an ample supply is not to be secured from wells properly made; this water is generally pure and wholesome. It is also of uniform temperature the year round—cool and pleasant in the summer, because the underground pipe and earth temperature remain uniformly low. In winter, well water being warmer than that taken from ponds and rivers, is not so apt to freeze, and, from all considerations of temperature and purity, well water is greatly to be preferred. Many cities located on rivers having a gravel bed formation find that, by placing wells of suitable construction far enough back from the bank, there is a natural filter bed, leaving the water clear, even when the river itself is muddy. When river or other surface water is good the wells may be sunk close to the edge, the water flowing down from the top of the wells.
There are not many underground formations where wells should be located close together. Such wells may affect or rob each other, and it is usually best to spread them out on a line across what is known to be the underground flow. Some finely creviced or tight rock formations have a strong head with but little capacity, and wells in such formations, if pumped hard, yield but little additional water. They should be scattered and pumped moderately, maintaining a low and economical lift. In other cases, one well in a group will give as much water as all together, and more territory must be drawn on.