Don't kid yourself. If you think polishing fuel at the dock does any
good your wrong. It's just about a total waste of time. Anything that
clogs the filters will hide in corners, stick to the walls of the
tank, and will not be removed by simply circulating fuel through a
filter over and over again. The only time a fuel polishing system
works if you get a high pressure return washing out every corner and
baffle and wall and roof and floor of your tanks, or you polish while
underway with a low enough fuel level, and seas high enough to beat
loose everything that clings on tight.

Just my take on fuel polishing systems.

Joe