resin or rubber the unitary diaphragm assembly 50 includes a flexible and sealing diaphragm 52 which has a mounting portion 54 at an outer peripheral edge the mounting portion 54 may be assembled into a u201c c u201d channel type gasket with reference to fig3 a sealing surface 56 is positioned at a generally radially inward position relative to the diaphragm 52 so as to cooperate with the main valve seat 20 of the flush valve an annular support 58 extends upwardly from the diaphragm 52 above the portion of the diaphragm having the sealing surface 56 radial reinforcing ribs 60 extend between the upper end of a barrel member 68 adjacent a relief valve seat 62 and the annular support 58 to reinforce the annular support 58 the relief valve seat 62 and the sealing surface 56 the vertical legs of the ribs 60 maintain the relief valve 28 of the flush valve in position so that it may seal against the relief valve seat 62 the reinforcing ribs 60 also extend to a flow ring 64 located on the barrel member 68 below the sealing surface 56 to add structural support for the flow ring 64 the relief valve seat 62 is positioned on the upper end of the barrel member 68 the.