All the water used in the hotel is filtered. The plant for this purpose comprises two Cummings filters made by the Cummings Filter Company, of Philadelphia. Through one is passed the water for the icemaking apparatus, the boilers, the culinary department, and for all other uses in the cellar, basement, and first floor. Through the other is passed all the water used on floors above the first. Each of these filtering tanks is composed of a 60-inch sectional cast-iron cylinder with bases and tops as shown in elevation and broken section in Fig. 10. The filters stand 9 feet 6 inches high. All the internal metallic surfaces are treated by the Bower-Barff anti-rusting process.

WATER FILTERS IN THE WALDORF HOTEL.

Water is delivered from the 4 inch Thomson meters through the 4-inch pipe A to the six way cock B. The line is then branched into the 4-inch pipes C C, which enter the tops of the separate cylinders E E. The cast-iron top plate F is dished so as to allow a 3-inch space between its upper surface, and a 3/16-inch galvanized-iron diaphragm plate which, with its packing, is inserted at the upper joints at G. This plate is perforated with 1/16-inch holes and has soldered upon its under side a fine meshed brass wire cloth. Three inches below this plate is a similar one, and between them is a 3-inch bed of clean-washed pea-size gravel H. At the bottom of the cylinders at joints S S are placed perforated plates, gravel, joints, etc. similar to those described at the top. Upon the top of the lower diaphragms is placed 4 feet of loosly filled-in animal charcoal, shown at I. The cock B being set for delivery to the filter sand the water turned on from the pipe A, it passes up C C and into the cylinders passing through the perforated plates and gravel bed. It fills the water space J and passes down through the charcoal I and through the lower plates and gravel to the pipe K leading to the pumps. The animal charcoal is heavier than water and consequently remains sufficiently compacted for filtering without compression. By closing valve L which controls the flow of filtered water to the pumps and turning the six-way cock B, filtered water from one of the cylinders may be passed upward into the other through pipe K for the purpose of washing the filter. This water passes in the reverse direction through the bed of charcoal and down through pipe C to the six-way cock by which it is directed into the waste pipe M leading to the sewer N. A single movement of the cock B will make the effluent of either cylinder wash the other.

Each of these cylinders occupies a ground space of 72x150 inches. The weight of each charged and ready for service is about 14 tons, of which three tons is animal charcoal. The plant is designed to filter 150,000 gallons daily.