A weir-type diaphragm valve includes a valve body having a spherically-shaped valve body sealing surface with a weir having a spherically-shaped weir sealing surface; and a diaphragm having a diaphragm sealing surface with a diaphragm weir sealing surface, the diaphragm responding to an applied force and providing sealing contact between the diaphragm weir sealing surface and the spherically-shaped weir sealing surface so as to stop the flow of fluid through a fluid flow channel of the valve body.