In the year 1908 the water department of the city of Auburn caused an examination to be made of the check valves of the mill and factory connections in the city of Auburn. And as these check valves were of the type that are bought on a competitive basis, and simply represented a design made looking towards an economy of material and labor, the results of this examination can be easily imagined. It was found in many cases that even the locations of the valves were unknown to the factory, and some had been buried in the ground for a period of twenty years, without ever having been examined. The final result of this inspection was that each and every mill or factory using city water for fire protection, and having a polluted auxiliary supply, was required to install double check valves of a special design, and to be placed in a brick or concrete vault, accessible at all times to inspection and test. The specifications under which the check valves were made, require that the seat ring, disc holding ring, and screws, and in fact all moving parts, and the hinge pin and bushings of samebe of bronze, the disc to be faced with medium hard rubber, and liberal clearance to be made all around the clapper, the pin, the arm, etc. These specifications were largely determined by the inspection department of the Associated Factory Mutual Fire Insurance Companies of Boston, and they also had to meet with the approval of the water department of the city of Auburn. The regulations are that they shall be tested once every six months by the water department, and taken apart once each year and examined for defects or obstructions, and during this latter inspection a representative from the Associated Factory Mutual Fire Insurance Company is present to observe the condition of the valve and assist at the test. It is specified by the water department that the inspection and test shall be at the expense of the factory or mill where the tests are made. Figure 1 shows a diagrammatic representation of an installation made in the city of Auburn. The stop gate valves A and D are so
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