Having recently bought a fuel filter as a precautionary measure, and having read in the owner's manual the chilling words, Fuel Filter, Draining Water: "For models with R9M engine, contact a NISSAN dealer or qualified workshop.", I was pleasantly surprised to find the following printed on the genuine NISSAN filter:
FOR WATER DRAIN
1. Turn on the key "Ign-on" position
2. Drain the water
3.Tight the drain plug with 1.2Nm - 1.5Nm. (which is about a ft.lb.)
The drain plug is below the diesel in and out connections and can be accessed by removing the guard frame, 2 × 13mm nuts. The plug takes a 22mm spanner. Best not to overtighten, but check afterwards for leaks.
I've read elsewhere that after changing the filter, one should turn on to "Ign-on" position for 30 seconds before starting the engine. Presumably this bleeds the system, but anyone better informed please correct me on this or any other details.