External wall tap valve comprising a valve body , the inlet-side line shaft of which has a line portion extended by several cm which, in the installed state, forms a line section that extends into the building wall, a rotary handle which is arranged on the side of the external wall tap valve facing outward in the installed state and is connected for conjoint rotation with a threaded sleeve which is mounted in the valve body and, at its end remote from the rotary handle , acts on a movable actuating rod with a closing element connected thereto, a valve seat which is arranged in the half of the line shaft in the valve body that is remote from the rotary handle , the closing element movable with the actuating rod forms, when in the closed position, a line closure in cooperation with the valve seat , and a system separator is arranged in the outlet-side end of the valve body in front of an outlet-side connector that has a flow valve which allows liquid to flow out of the valve body and blocks an inflow of liquid from the connector into the valve body , the threaded sleeve is held with its external thread in a valve-body-side internal thread so as to be rotatable in an axial direction (A) and has a receiving space in which a valve pin movable in the axial direction (A) is arranged, which pin is held under pressure in a first position relative to the threaded sleeve against a valve seat formed in the receiving space by a spring which is located in the receiving space and is compressible in the axial direction (A), in the receiving chamber an annularly circumferential constriction of the inner diameter to the adjacent inner surface of the receiving chamber is formed, against the surface of which the valve pin sealingly abuts in its first position with a sliding seal arranged on the valve pin , in a first screwing-in movement of the threaded sleeve into the valve body , the valve pin located in the threaded sleeve moves the actuating rod from an open position into a closed position in which the line closure is closed, in the closed position of the actuating rod said rod forms a stop for the valve pin , by which the valve pin is blocked against continued movement in the axial direction (A), after a second screwing-in movement continued beyond the first screwing-in movement, the threaded sleeve is displaced against the spring force of the compressible spring and the valve pin is pressed deeper into the receiving space , in which the valve pin is located in a second position relative to the threaded sleeve , in the second position the sliding seal is pushed out of the annularly circumferential constriction of the inner diameter and a flow channel is released between the valve pin and the annularly circumferential constriction , the threaded sleeve has drainage openings , in its portion facing away from the annularly circumferential constriction of the inner diameter in the direction of the rotary handle , for draining the receiving space , and a flow channel is formed between the valve pin and the inner surface of the receiving space of the threaded sleeve , which channel connects the interior of the valve body to the draining openings in the second position of the valve pin . <EOS>