First I drain the water separator at the CAV prefilter and then I replace the CAV filter unit.
After a successful refilling of the prefilter unit I change the fine dieselfilter and vent out the system.
To make the venting go faster you can fill the finefilter with diesel and put a finger to the vent hole at the fine filter while pumping.
The pump will then suck up the diesel from the prefilter via the created vacuum and on that way it will go much faster.
When the diesel has almost reach the top at the vent hole at the finefilter you can pump out the rest of the air and then close the hole with the screw.