A diaphragm valve comprises a body having an inflow passage, outflow passage, valve chamber and valve seat, a metallic diaphragm for maintaining air-tightness of the valve chamber, a bonnet for securely holding the edge portion of the outer circumference of the metallic diaphragm in cooperation with the body, a stem inserted through and supported by the bonnet but movable up and down, and a valve disk inserted through a center opening in the metallic diaphragm. The valve disk comprises a seat portion of disk-like shape contacting with and moving away from the valve seat, a shaft portion provided on the top surface of the seat portion and inserted through the opening in the diaphragm, and a connecting portion provided at the top end of the shaft portion and connected to the bottom end portion of the stem. Water Power Control ValvesAn end edge portion of the inner circumference of the diaphragm is welded to the disk valve shaft portion over the entire circumference of the shaft portion at a location spaced from the seat portion so that a large gap exists between the upper surface of the seat portion and the lower surface of the diaphragm, thereby improving gas substitution performance. Water Control valves

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