Water Separator -2005 Jetta TDI

It looks like a really big oil filter with four hoses attached to it. Likely it will be on the side of the engine compartment shoe horned in somewhere. There will likely be a white plastic wheel on the bottom which you unscrew some to allow maybe a ¼ cup of fuel-water to drain and then re-tighten. It may take a little longer to start the next time you try to start it. Having long fingers and very small hands is a plus.

These people have much better and detailed instructions