Abstract: A liquid integrator apparatus for insertion into a liquid flow line, for blending together leading and lagging incremental liquid flow volumes, the apparatus including a housing attachable to the liquid flow line, a cylindrical insert in the housing, the insert having a helical groove about its outer surface. The helical groove is substantially deeper than it is wide, and has a hydraulic radius of less than about 0.04, and the helical groove is sufficiently long so as to contain a liquid volume approximately twice the volume of incremental liquid for which blending is desired.