Agree with comments that it's better to agitate with fuel rather than air.
Getting effective action would seem to call for an additional pump (high
volume) and separate pick-up and return line. Many boat owners won't want to
add this expense and complication to their polishing systems. On the other
hand, a small air compressor or inflator is more apt to be available.

As the return line usually enters at the tank bottom, just circulating fuel
at a high rate before starting polishing and periodically will help. A high
output pump with filter bypass valving can be used for dual purposes -- a
small volume of fuel goes through filter (with check valve on output),
while most bypasses it and enters the return inlet with force.

Another polishing approach is draw fuel from a bottom return line and return
it tank via fill fitting. The theory here is that most of the bad stuff is
near the bottom
--
Eliminate "ns" for email address.
"Rich Hampel" wrote in message
...
In article , Len Krauss
wrote:


Second step is to, while polishing, agitate fuel at bottom of tank using
a
small L-shaped air discharge pushed down to tank bottom on a rod or
dowel
and turned about as much as possible. Obviously the fuel furthest away
from
the discharge will get the least agitation and baffles will reduce
degree of
agitation for sure. But with the L-shaped discharge at the bottom and
turned, disturbance will flow through baffle bottom notches. The basic
idea
is to get crud in suspension and moving so it can be captured by the
polishing pick up and filtered out.


You are correct!!!! but dont use air.

Tank farms use whats known as a *sparging nozzle* to keep the tank in
constant agitation. Its simply a jet of liquid that discharges into a
throat of a venturi section. The velocity from the jet into the
venturi 'entrains' the liquid in the bottom of tank to circulate. A
sparger moves the layers on the bottom of the tank towards the top;
hence, affects a mixing.
(for techies amoung us, a sparging nozzle {sparger} in an 'open inlet
eductor')

If you use air, you generate a lot of air entrainment which can settle
out and coalesce into larger and larger bubbles of air .... and block
the downstream system.