Abstract: In a stop or switch valve of the type having a valve head (76,78) mounted on a reciprocable valve rod (86) the bushing member (30) as guiding the valve rod is provided with a cylindrical recess (48), through which a cleansing or sterilizing medium is brought to flow for counteracting contamination of the valve liquid when the valve head is switched into a position, in which the previously retracted valve rod portion (86, 74) is reintroduced into the valve chamber (4,6) as holding or conducting the valve liquid. The recess (48) is flow connected with further recesses or channels (52, 106) as provided adjacent the outside of such sealing rings, which seal various other valve chamber wall portions (30, 76, 88), whereby the recess or channel systems can be included in a leakage supervision arrangement.