A device is described for combined fluid replacement and pressure testing in pipes with inaccessible end points. The device is characterized in that it is a two-piece circulation valve structure comprising: a first valve unit (4) comprising a seal element (1) which closes and opens depending on the dynamic fluid pressure through the valve, and a second valve unit (6) arranged to permanently close off the fluid flow when the pressure testing terminates. The first valve unit (4) comprises an elastic sealing ring (1) arranged to close against a seat in the valve unit in step with an increase in the fluid flow velocity through the valve, while the second valve unit is a casing (6) which is arranged inside the valve an closes when a pressure differential arises between a chamber (7) and the inside of the valve (4).