Well, it seems that racor fg 500 filters require 60 GPH flow to separate particulate and water properly. I don't know what engine pushes 60 gallons of fuel past the injectors per hour, certainly not mine. (perkins 4 - 108) (i doubt it would be 1 gallon) Therefore I need an electric fuel pump to polish my fuel while the motor is running. Fuel pumps can deliver this kind of flow, (60 gph, 5psi) and you polish your fuel through the dual racors. I change filters regularily and have a vacuum guage on each low pressure side of racor. When it starts drawing -12hg, it's filter time... I have 2 tanks that are selected by one 6 way valve that is either tank 1, tank 2, or off. The only other valve to open or close is a relief valve (WOG ball valve) from the pressure side of the system into the return line of the tanks (2 - 75 gal). The system is as simple as it can be made, while being able to polish both tanks. If I were to add some valves, I would add the ability to transfer from tank to tank. Till then I will just switch the hose
So I would like to know what kinda pump you think I should throw in it?