Hello. I would recommend that you remove the fuel filter and filter mount as a unit......tie the hose from the filter to the IP up so as not to lose the fuel in the line...........remove the water detector and install it into the new filter......fill the new filter with diesel and let it "soak in".........now clean the filter mount well as it has a one way valve in it........check it to make sure you can only blow one way through it..........keep filling the new filter until it will not take any more fuel........screw the filter to the mount and reinstall.......make sure the line to the IP is full of diesel and install................I also recommend to remove the fuel tank top and to blow compressed air back through the fuel line that goes back to the tank......................

This would also be a good time to clean the screen at the banjo joint where the metal fuel line connects to the IP.............just reinstall and fill the hose and line with diesel............

regards,
crossbones