Such a system can be cheap and effective...
Hello, Steven...Bob's approach beats what most owners do, or rather 'don't do'. But I found a number of boats using a system such as you describe in the Caribbean, where fuel arrives at the end of a questionable supply chain and is stored in sometimes questionable circumstances. I'm going to adapt the dual Recor filtering system I have, including an in-line simple/cheap electric fuel pump I previously installed to aid in bleeding my engine's fuel system, to do just what you describe. This will only require me to add a 'T' valve, directing the fuel exiting the on-service filter to return, via a second 'T', to the return line to the tank.I don't think this is a total 'fix' as it doesn't immediately guarantee you'll be pulling out that mixture of debris, water, etc. that Bob got to with his targeted approach. But not all the algae and dirt contained in fuel is at the tank's bottom, and the stuff that is there doesn't always remain there. Algae exists thru-out the tank, attached to the walls and baffles, and is placed in suspension as the tank empties and the boat finds itself in active sea conditions. Suspended water & dirt also exists in the fuel sometimes being taken onboard the boat (and certainly within the U.S., not just outside it). That's when the cleaning ('polishing') system you ask about comes into its own. Immediately after refueling or following a rough passage and with the tank level down a bit both seem to me to be ideal times to switch on the fuel pump, throw the valve, and circulate the fuel thru the filtering system. Even a small pump, drawing less than an amp, will push a gallon a minute. Cycling 50 or 100 or 150 gallons of recirculating fuel thru a 2 micron Racor filter can do a lot of cleaning for the cost of a few amp/hrs and a single Racor filter element. Folks who were using this in the Caribbean swore by it, and never suffered from the problems of fuel contamination.One cavaet: if the standpipe they installed in your fuel tank has a screened cover - a common practice until the 90's - none of this will prevent that pipe from eventually clogging up with debris. This happened to our tank, over time and, with no access to that standpipe without pulling the tank, I ultimately had to use the dink's foot pump to blow out the standpipe's blockage after much plumbing work over a hot but fuel starved engine. It wasn't a great way to spend a rough day in the Mono Passage off Puerto Rico; I think a polishing system will help me avoid this a second time.Jackjack_patricia@yahoo.com