Abstract: A fluid circuit sealing apparatus having a valve body with a valve base having a fluid inlet pipe and a fluid discharge pipe extending therethrough, a diaphragm having a cup shape, and a piston engageable with the diaphragm so as to deform the diaphragm so as to rest upon a seat provided on a rim of the inlet pipe. The diaphragm is clamped on an edge thereof between the valve body and the clamping cover. The diaphragm has a raised circumferential rim which forms an angle with a bottom of the diaphragm. The diaphragm has a parabolic dome. The raised circumferential rim has a circular upward fold portion extending to a slanting annular portion. The slanting annular portion is connected to the parabolic dome by a circular fold. The circular fold extends around a periphery of the parabolic dome.