As a bystander your comments make interesting reading. I’ve often thought about making such a rig, perhaps an ideal over-winter project.
I don’t use a lot of fuel over an average U.K. season, I tend to keep the tank full and (infrequently) use Millers bug treatment.
Why do you have to re-polish every two years? Do you consume a lot of fuel? Dodgy filling stations? Just bad luck?
I top up the tanks approx twice a season which probably equates to one full thankful used per year. So not big usage and that's one of the main problems. But as I can't get to physically clean the inside of my tanks there is a residual contamination issue which I can only manage by regular treatment and polishing.
I treat with bug killer every time I fill, last year it was Marine 16 and this year it's been something else sold at my marina. Best to change periodically to prevent resistance, is the perceived wisdom.
Yet despite the above I have found some contamination lurking in the bottom after a couple of years.
I think it's now a fact of life as a result of the FAME content in modern fuel, which permits and may already have moisture in it when you fill up. But it's not a big problem now I have my polishing rig and it's just good practice to keep on top of things.
What size filtration do you use?
I use a Fleetguard filter that importantly removes 95% of engrained and dissolved moisture as well as particles etc. There is often great play and emphasis on "5 micron filtration" or whatever but unless you have one of the latest common rail diesels the micron figure is a complete red herring; removal of moisture is the key aim. Need to remove the bug's habitat so it can't exist. So whatever filter you buy make sure the moisture removal figure is quoted. If it's not quoted then it won't do the job; not all filters do by any means.
TIA
(Well worth a quick read IMO) (Tech document prob of little interest)