Valve insert for a sanitary fitting

A valve insert for a sanitary fitting can be inserted as an insert into a recess in the housing of the sanitary fitting and interacts there with lines of the sanitary fitting that open into the recess. The valve insert contains a base element which receives and holds the moving parts of the valve contained in the valve insert. An adapter element which is preferably injection-molded from plastics material and contains a valve inlet opening and a valve outlet opening can be connected in an exchangeable manner to this base part. The openings interact with the lines that open into the recess. A water guide leads from these two openings to the valve. By exchanging the adapter element, the valve insert can be used for different applications. Preferably, the valve seat itself can also be arranged in the adapter element.