Adding A Fuel Polishing Diversion Loop

[aybabtme]

I've had some issue with my diesel tank getting dirty with water and growth, despite taking care with keeping the tank full and with biocide when leaving the boat for long periods. The boat came with a Racor 115 primary filter, which I find makes it hard to debug since it doesn't have a see-through bowl. So I'm upgrading the filter with a Racor 500MA.

As I'm installing the new filter, I was also removing an old diesel line that was left from PO for a diesel heater. This part of the system had a Walbro 2402 pump on it, so it got me thinking about reusing the pump and some fittings to create a diversion polishing loop. The pump doesn't appear to work, but I nonetheless want to try and add a diversion loop in the system that would pump diesel through the Racor 500MA on a schedule when the engine isn't running, to try and keep fuel in the tank as clean as possible.

Here's what the current fuel line looks like:

And here's what I have in mind:


Notes:

• the Racor 500MA is rated for 60GPH, a max allowable pressure of 25PSI and creates a pressure drop of 0.25PSI when clean. Docs.
• I'm thinking of getting one of the Walbro FR line pumps.
• The fuel lines are 1/4".
• Power is not an issue. I can dedicate 100Ah to this per day without a problem.

Do you see any problem with this design? Should I have some check-valves on the return lines? Do you recommend a specific pump?