"When it comes to pre-filtering oil, the SVO folks are the experts, regularly filtering down to 5 and even 1 microns. If oil is first filtered to 10-30 microns then heated to about 80-90F and held there in an insulated drum for 8 hours, the top 2/3 will be water free. Co-ops tend to heat the oil first and filter while hot using pumps for speed. Some will use centrifugal separators, again for speed. Centrifuges may also hold promise for removing FFA's. Most individuals, however, seem to be using gravity filtering the oil before heating and settling because of the ultra low cost and simplicity."