DISCUSSION: TESTING OF CHECK VALVES

Mr. J. Walter Ackerman: The check valves we use are designated by the underwriters as a "special sanitary check valve." There are two or three forms that are being made and have passed the underwriters' test. The principal difference is that the valves are made in tandem, or at least they are assembled in tandem, with sufficient clearance between them so that any ordinary stick or anything of that sort that might get in the mains would not keep both of them open at one time. All the moving parts, the seat ring, the clapper, the arm of the clapper, the hinge pin and the socket of the hinge pin are bronze, with a rubber seat; the rubber being somewhat like that used in the Grinnell dry valves. The clearance is also made very liberal so that any of the tuberculations on the inside would fail to reach the clapper, so that it would always be perfectly free. The inside of the valves is also coated with some sort of asphaltum paint or similar product to prevent tuberculation as far as possible. A letter to the underwriters will give you a list of the manufacturers that make these "special sanitary check valves/' showing what ones have been O.K'd by the underwriters.