A sanitary fitting (1) formed from a multi-wall housing (2) which can be inserted into a sanitary water pipe is provided that has at least two adjacent walls (6,7) surrounding an inner region (8). The fitting includes a checj valve , and one wall of the housing (2) is a tubular wall (7) formed of a flexible and/or elastic material. In order to relieve pressure when the check valve is closed and the fluid volume is sealed in on the outflow side, the housing wall (7) can be moved towards the adjacent housing wall (6), compressing the at least one inner region (8), or can be spaced apart from the adjacent housing wall (6) or moved away from same, enlarging the at least one inner region (8).