Water Separation Characteristic, Free Water And Particulate Testing (ASTM Standard Test Methods D3948, D7224, D7261 & D4860)(D3948 is included in Specifications D1655 and D7566) 

 For quality control purposes, water separation characteristics of fuels are rated to determine the amount of surface active materials (surfactants) present. Surfactants degrade the performance of filter separators used to remove water from the fuel.