A selector valve of a pressure filter for aquariums or ponds comprises a valve body having a main liquid inlet opening (16), a secondary inlet opening (17), an outlet opening (18) and a discharge opening (19), a cursor (20) housed in the valve body (12), having a passage for the liquid (21) and being selectively moveable between a first position, corresponding to the filtration mode of the filter (11), wherein the main liquid inlet opening (16) is placed in fluid communication with the outlet opening (18), and a second position, corresponding to the washing mode, wherein the secondary inlet opening (17) is in fluid communication with the discharge opening (19), and a safety valve (36) included in the cursor (20) to protect the pressure filter in case of overpressure of the liquid.
