An apparatus for controlling a fluid flow in, into or out of a well, the apparatus comprising: - a main flow channel having an inlet and an outlet being in fluid communication with the fluid flow; - at least one chamber forming part of, or connected in fluid communication with, the main flow channel , the chamber configured for housing at least one flow control element movable between a first position where the flow control element does not block the fluid flow between the inlet and the outlet of the main flow channel , and a second position within or outside of the chamber wherein the flow control element blocks the fluid flow between the inlet and the outlet of the main flow channel , the flow control element movable in response to density of fluid in said chamber, characterised in that : - the main flow channel is provided with pressure changing means comprising an expansion section arranged in the main flow channel , the expansion section having an inlet with a smaller cross sectional flow area than a cross sectional flow area at an outlet, the pressure changing means providing a pressure differential in a fluid return conduit extending between said chamber at a location wherein the flow control element is in the non-blocking position and a portion of the main flow channel being within or upstream of the pressure changing means , so that fluid in said chamber is recirculated back to the main flow channel when the main flow channel is open. - a main flow channel having an inlet and an outlet being in fluid communication with the fluid flow; - at least one chamber forming part of, or connected in fluid communication with, the main flow channel , the chamber configured for housing at least one flow control element movable between a first position where the flow control element does not block the fluid flow between the inlet and the outlet of the main flow channel , and a second position within or outside of the chamber wherein the flow control element blocks the fluid flow between the inlet and the outlet of the main flow channel , the flow control element movable in response to density of fluid in said chamber, characterised in that : - the main flow channel is provided with pressure changing means comprising an expansion section arranged in the main flow channel , the expansion section having an inlet with a smaller cross sectional flow area than a cross sectional flow area at an outlet, the pressure changing means providing a pressure differential in a fluid return conduit extending between said chamber at a location wherein the flow control element is in the non-blocking position and a portion of the main flow channel being within or upstream of the pressure changing means , so that fluid in said chamber is recirculated back to the main flow channel when the main flow channel is open. - the main flow channel is provided with pressure changing means comprising an expansion section arranged in the main flow channel , the expansion section having an inlet with a smaller cross sectional flow area than a cross sectional flow area at an outlet, the pressure changing means providing a pressure differential in a fluid return conduit extending between said chamber at a location wherein the flow control element is in the non-blocking position and a portion of the main flow channel being within or upstream of the pressure changing means , so that fluid in said chamber is recirculated back to the main flow channel when the main flow channel is open. <EOS>