Subsea separation of produced water increases the recovery rates for brown field installations. Removing produced water on the seabed increases production rates, removes topside produced water bottlenecks and enables better utilization of existing topside facilities. Existing subsea bulk water separator technologies are limited to gravity and compact gravity vessel types, as seen on Troll and Tordis, and the pipe separator installed at Marlim, which are large, heavy and costly installations. In order to make the business case for subsea produced water separation more attractive, there is a need to reduce the weight and areal footprint of separator designs. It is also important to develop separator solutions that can be qualified for a wide range of field operating conditions.This paper presents the experimental testing of a novel produced water separator design, the Multiple Parallel Pipe Separator (MPPS). The design uses multiple horizontal pipe segments in parallel for liquid-liquid separation, with inclined outlet pipe segments for increased water holdup and eased water extraction. Experiments are performed on a two-pipe prototype.A limited test matrix was run to investigate the best location for water extraction. Three tapping locations were tested. Experiments displayed oil re-entrainment along the inclined extraction pipe, and the best extraction point was found to be close to the horizontal to inclined transition.Using the identified tapping location, a detailed performance mapping was performed at total flow rates from 300 to 700 L/min and water cuts ranging from 30 to 90%. The performance mapping was performed with three different inlet configurations, a normal inlet, a tangential inlet, and a tangential inlet accompanied with novel phase re-arranging internals. Best separator performance was achieved for the tangential inlet with internals configuration, displaying efficiencies in the range 78.8–100%.A dispersion layer was observed in the separator pipes for total flow rates above 350 L/min. At low water extraction rates, this forming dispersion layer was observed to migrate completely into one of the two separator branches at random. The uneven splitting of the dispersion layer was observed to strengthen when changing from a normal to a tangential inlet configuration. The installation of phase-rearranging internals eliminated the uneven splitting of the dispersion layer, resulting in an even phase distribution between the two separator branches.