A trick I learned as a Bush Pilot in Alaska. Works with gasoline, don't
know about diesel.

With gasoline, pour it through a chamois (pronounced "shammy") skin
(sheep/goat skin you get at your FLAPS or Wally World - auto section).
The skin - a real one that is - while being leather, is very porous, and
gasoline will pass right through, while leaving water and contaminants
behind trapped on the surface of the skin.

All bush pilots used this trick when fueling from cans, drums, and other
suspicious sources out in the bush country. Never trust fuels under
those conditions to be water and contaminant free. Always strained it
through a chamois when fueling. Just a few drops of water could cause
one to have a really bad hair day with and engine failure on takeoff
over a cliff or out over the water or over the river when taking off
from a river sandbar.

Tough to make emergency landings in those places. At very minimum a few
drops of water in the gas could give you white-knuckle fever and/or
cause the pucker factor to go off the scale and leave a permanent cone
in the seat cushion that even the very best brand of cone remover would
not remove.

Regards,

John Rodgers
88 GL Driver