Fuel polishing

We happened to have a "professional" fuel polisher working our marina last weekend. He had a fancy machine that consisted of a big drop in paper filter and a strong pump. He said the secret is to send the return fuel back to the tank under high pressure, 30-40 psi. That keeps the tank stirred up and all the crud in suspension. Worked about 4 hours on an unaccessable 30 gallon tank. Went through 5 filters before he got one that remained clean after 30 minutes of circulation. He admits it is not as good as a mechanically cleaned tank, but for those tanks that cannot be easily cleaned it is a very viable alternative.