Abstract: An improvement in a check valve, especially a check valve intended to be mounted across a corresponding opening of a hydromassaging apparatus. The check valve comprises a casing having an inlet and an outlet, a conduit extending from said inlet to said outlet, structure for axially setting and fastening the check valve in a corresponding opening, and improved structure including a membrane and consisting of a flexible membrane made of elastomeric material and provided with an orifice, an element provided with a flap seat of sufficient size to completely cover the orifice, structure for connecting the element with the casing and positioning the seat in the vicinity of the outlet, and structure for fastening a periphery of the membrane across the outlet of the casing, to align the orifice with the seat and to position said orifice in such a way with respect to the seat that the elasticity of the membrane presses a portion thereof surrounding the orifice against the seat.