What is the best way to remove water from hydraulic oil?

The oil purification system probably the best way to seperate just about anything, the problem with water in hydraulics is that it doesnt get chance to settle because the system is constantly turning over oil, then you get the milky crap.  you can get water seperation filters and our company come and do it for you but our oil filtration equipment has to be  operating, the oil filtration machine can do it on line and while operating, be careful because it does seperate some of the additives as well. 

These are used today to seperate vegetable oils from the raw fibres, and same with grain oils, they remove dirt very well in hydraulic systems.