A separation type multiphase flow meter apparatus (1; 10) comprising a separation module (8; 18) arranged to at least partially separate a multiphase stream comprising water, hydrocarbon liquid and hydrocarbon gas into a first sub-stream comprising a gas fraction and a second sub-stream comprising a liquid fraction, wherein the apparatus (1; 10) further comprises: - a first metering device (6; 16) for measuring the flow rate of the first sub-stream; and - a second metering device (7; 17) for measuring the phase fraction and the flow rate of the second sub-stream, wherein the second metering device (7; 17) is arranged to measure the water-in-liquid ratio of the second sub-stream, wherein the apparatus (1; 10) is arranged to use the water-in-liquid ratio measured by the second metering device (7; 17) as a measure also for the water-in-liquid ratio of the first sub-stream, and wherein the cross-sectional flow area of the first metering device (6; 16) is larger than the cross-sectional flow area of the second metering device (7; 17) wherein the separation module (8; 18) comprises: - an inlet conduit (2; 12) configured to receive, at an inlet, the multiphase stream; - a first measuring conduit (4; 14) configured to receive, from the inlet conduit (2; 12), said first sub-stream, in which first measuring conduit (4; 14) the first metering device (6; 16) is arranged; - a second measuring conduit (5; 15) configured to receive, from the inlet conduit (2; 12), said second sub-stream, in which second measuring conduit (5; 15) the second metering device (7; 17) is arranged; and - an outlet conduit (3; 13) configured to receive the first sub-stream from the first measuring conduit (4; 14) and the second sub-stream from the second measuring conduit (5; 15), and to output, at an outlet, the re-joined multiphase stream, characterised in that the first measuring conduit (4; 14) extends orthogonally or substantially orthogonally from the inlet conduit (2; 12); and wherein, when the apparatus (1; 10) is in operation, the inlet conduit (2; 12) is configured to have a horizontal or substantially horizontal orientation and the first measuring conduit (4; 14) is configured to extend vertically upwardly or substantially vertically upwardly from the inlet conduit (2; 12) allowing the first sub-stream to be conveyed vertically upwardly or substantially vertically upwardly in the first measuring conduit (4; 14), and allowing the second sub-stream to be conveyed horizontally or substantially horizontally in the inlet conduit (2; 12) downstream of the first measuring conduit (4; 14). - a first metering device (6; 16) for measuring the flow rate of the first sub-stream; and - a second metering device (7; 17) for measuring the phase fraction and the flow rate of the second sub-stream, wherein the second metering device (7; 17) is arranged to measure the water-in-liquid ratio of the second sub-stream, wherein the apparatus (1; 10) is arranged to use the water-in-liquid ratio measured by the second metering device (7; 17) as a measure also for the water-in-liquid ratio of the first sub-stream, and wherein the cross-sectional flow area of the first metering device (6; 16) is larger than the cross-sectional flow area of the second metering device (7; 17) wherein the separation module (8; 18) comprises: - an inlet conduit (2; 12) configured to receive, at an inlet, the multiphase stream; - a first measuring conduit (4; 14) configured to receive, from the inlet conduit (2; 12), said first sub-stream, in which first measuring conduit (4; 14) the first metering device (6; 16) is arranged; - a second measuring conduit (5; 15) configured to receive, from the inlet conduit (2; 12), said second sub-stream, in which second measuring conduit (5; 15) the second metering device (7; 17) is arranged; and - an outlet conduit (3; 13) configured to receive the first sub-stream from the first measuring conduit (4; 14) and the second sub-stream from the second measuring conduit (5; 15), and to output, at an outlet, the re-joined multiphase stream, - an inlet conduit (2; 12) configured to receive, at an inlet, the multiphase stream; - a first measuring conduit (4; 14) configured to receive, from the inlet conduit (2; 12), said first sub-stream, in which first measuring conduit (4; 14) the first metering device (6; 16) is arranged; - a second measuring conduit (5; 15) configured to receive, from the inlet conduit (2; 12), said second sub-stream, in which second measuring conduit (5; 15) the second metering device (7; 17) is arranged; and - an outlet conduit (3; 13) configured to receive the first sub-stream from the first measuring conduit (4; 14) and the second sub-stream from the second measuring conduit (5; 15), and to output, at an outlet, the re-joined multiphase stream, characterised in that the first measuring conduit (4; 14) extends orthogonally or substantially orthogonally from the inlet conduit (2; 12); and wherein, when the apparatus (1; 10) is in operation, the inlet conduit (2; 12) is configured to have a horizontal or substantially horizontal orientation and the first measuring conduit (4; 14) is configured to extend vertically upwardly or substantially vertically upwardly from the inlet conduit (2; 12) allowing the first sub-stream to be conveyed vertically upwardly or substantially vertically upwardly in the first measuring conduit (4; 14), and allowing the second sub-stream to be conveyed horizontally or substantially horizontally in the inlet conduit (2; 12) downstream of the first measuring conduit (4; 14).