Why aren't "fuel polishing" systems removing water & ice from fuel in aircraft, like in cruising yachts? Should you sump fuel tanks when the fuel system is below freezing? the question

should one sump fuel-tanks before flying, if in freezing-conditions?

but this implies another question that boggles me:
Why don't aircraft have &quot;fuel polishing&quot; systems, to remove water from tanked fuel, especially since the cost of having a line block with ice, is so horribly high?
Cruising boats sometimes have such things, &amp; given the peace-of-mind it'd give, why aren't these devices in play, in aviation??
( btw, it essentially is a filter &amp; water-bypass thingy, so the water goes to the bottom of the glass bowl, &amp; the fuel, above that, goes through the filter, if they combine them, or maybe the water-separator &amp; the filter-unit are separate, in sequence, but both are present, before the fuel goes anywhere near the engine... )
I believe a fuel polishing system is run before firing-up an engine.
This removes all the contamination before the engine's fuel-pump even starts.
edit 2:
Marine Diesels, in the stuff above...
Also, this is in light of some events written about years ago...
1 was a small jet that lost power at high altitude due to slush-ice in fuel,
another was a jetliner that smashed after the same problem, ttbomk...

slush-ice in the fuel clogged something in the fuel-system, causing...

a drop in power, so therefore the crew...

increased thrust, which caused ALL the engines to clog/die, so the new recommendation was...

if in that type, at high altitude, in cold, if power reduces unexpectedly,
then reduce thrust to unclog the lines, &amp; it should clear...


also many apparently have had problems with ice in fuel messing things up for them in piston aircraft...
also I know some are running automotive-conversions,
&amp; if anyone ever has ethanol-blend gas in their aircraft,
&amp; that ethanol has absorbed water, &amp; gets cold, it can separate out,
leaving 2 distinct fluids in the tank:
ethanol-water &amp; gasoline.
( I'm not saying running auto-fuel is legal in an aircraft,
but rather that I know human-nature. )
edit 3:
that link above includes some interesting stuff
also, the whole idea may be bunk,
if the amount of ice-slush in a jetliner's tanks is measured in tonnes, rather than litres,
as no catching-out device is going to handle that kind of volume.
I don't know what volume is involved.
The simple answer is weight/risk/added complexity: the systems are heavier than they are worth for the problems they avoid in aircraft.
While ice blockage has been an issue for aircraft in the past, planes that fly high enough to warrant it have fuel heating systems to avoid this very issue.
The reality is that the chances of water getting into marine fuel are MUCH higher than water getting into AvGas. Water finds its way into airplanes in mainly one way: warm moist air that fills the space in fuel tanks condenses in the cold and the water precipitates out. This often happens over night when planes are not re-fueled after their last flight and left out in the cold. As such its extra important to sump the tanks for the first flight of the day. You can also mitigate this by filling the tanks every night if possible. Pilots are also taught to diligently sump tanks to avoid the issue in the first place.
In my experience, flying in the north east of the US where the air can get humid and the nights can be cool, I've never pulled more than a few bead size drops of water out of the tanks of my archer in the morning. I know of others that have pulled more but not significantly more.
There have been occurrences of a fair bit (hundreds of gallons of water) getting into aircraft tanks but these have generally been caught and handled. On the bright side we have a few nice things in aircraft that make water easy to deal with.

Water is heavier than AvGas so it will pool at the lowest point of the tank which is generally where the outlet/fuel line is connected.
The lowest point of a fuel tank on an aircraft is fairly easy to get to so pulling a test sump of fuel is no problem during pre-flight
It's fairly easy to deal with the fuel once it's in the sump cup on the ramp, chances are you wont anger the EPA all to much.

On the contrary, with marine fuel tanks it can be hard, if not impossible, to access the sump in any reasonable way and once you drain it you run the risk of it getting in the bilge and ending up getting pumped overboard which the EPA will have an issue with.
On a boat you have lots of options for water to get into the tank since there is generally water all around. Maybe it splashed in some gas cans you had on deck, maybe it splashed in during a mid trip re-fuel, maybe it splashed in refueling at a dock, maybe it was raining one of these times or all of these times, maybe the dock kid put the fresh water hose in the fuel inlet in a haste etc. etc. As such fuel/water separators are far more critical on a boat where there is often space and weight to spare and the chance of water getting into the fuel is high.