I use a GE whole house filter system to filter my home made wines. Ive used spun Polypropylene ,wound Polypropylene, pleated paper, and string wound. Mostly I use 5 micron filters but Im noticeing quite a difference in how much vacum is required to draw the wine through the different filters even though they are all 5micron rated. My vacum source is not strong enough to pull through the spun polypropylene filters at all. Obviously its the material that is causing this. Pleated paper are also a challenge to the vac pump. Can some one explain why the differences? The string wound filters require the least vac but Im wondering if they are as efficient as the others.