Give each of the knobs an egual number of turns and in the same direction. Turning the knobs clockwise, or to the right, inc~eases the pressure necessary to operate the valve. Turning the knobs counter-clockwise, or to the left, lowers the pressure necessary to operate the valve. Tests conducted on a number of modified valves in a valve test chamber determined that ten complete turns on each of the three knobs changes the pressure setting necessary to oper› ate the valve by 1/5 of an inch of H 2 0. 

After a satisfactory resetting is found, add. leather washers and screw the sealing caps in place again, then safety the knobs to the clips on the shield. Test setting against the air manometers. The use of the gas manometer is misleading, except at, or very near, pressure height. 

