A pipe network having an area where one planar bifurcation is followed by a second planar bifurcation. The planes of the two bifurcations are not coincident. This reduces non-uniformity in wall shear rates at the exit pipes of the second bifurcation. Preferably, the plane of the second bifurcation is rotated relative to the plane of the first bifurcation. In an alternative form, the pipe network has a planar curve followed by a planar bifurcation, with the planes of the curve and the bifurcation not being coincident.