To make sure my glow fuel will stay good I take extra care to make sure the jug is sealed tight in between fuelings to reduce the probability of moisture getting into the fuel. I do a pretty good job because sometimes a lull in flying happens for a few weeks and my fuel seems just as fine as the day I opened the jug.

When done flying for the day I de-fuel the plane trying to get as much out of the tank as possible so it too doesn’t collect moisture and taint the next flight, whenever that may be.

Tonight I’m done flying, de-fueling my plane, the fuel pump is running in reverse and I’m tipping the plane to get all fuel and the clunk to one corner trying to get as much fuel. This point it’s mostly sucking air. I look at the fuel jug and it dawns on me that I basically aerating my glow fuel. So during this de-fueling process I’m super injecting something I try very hard to keep out… Moist air.

Any thoughts on this?

I defuel into another fuel tank which I carry with me in the flitebox. Inside that tank one line goes to the bottom and the other line is short. Attach your drain line to the storage tank line that goes all the way to the bottom. (otherwise you'll have a mess) Then for the first flight of the day, attach your fuel line to the short tank line& turn the tank upside down & eithe rlet it drain or block off the appropriate line and squeeze. To store it just hook both lines together.
That way you are using all your fuel and getting rid of the old fuel with the first flight. And you don't contaminate your fuel jug with burned residue & humid air.
I had flameouts when near the end of the jug of fuel until I started using this method.

I've always drained my tanks back into the jug from which they were filled.

While it might seem like a bad idea to do this, stop and think for a moment.

If the moisture from the exhaust pressure was *really* contaminating your fuel, wouldn't the fuel in the tank itself have been really fouled by the time you get down to half a tank or less?

How come my engines still run just as well on the second half of a tank-full as they do on the first.

I think the problem of draining the dregs of your tank back into your fuel bottle is *way* overstated and in practice there is *zero* effect.

Actually, I've HAD problems with the fuel drained back into the main fuel jug. I don't think it's the humidity as much as the waste resdue ie., oil from the aircraft tank. the % of oil is higher, there are unburnt hydocarbons, ect.
I was having a problem with a relatively new engine and of course had 1000 different suggestions from those at the field, one guy came up and offered his new fuel jug. Problem solved!!!! The engine worked beautifully.
Anyways, since I started using the small storage tank & burning off the old fuel on the firrst flight I've never had anymore engine "problems". And, I've been doing this for over 25 years. so experience wins over "thinking"
It is NOT overstated.

Prairie Mike good point and good suggestion too. For a couple decades now I’ve been using a small fuel tank when fueling to catch over flow out of the vent line, figured I capture more than half a tank of fuel for every gallon, instead of letting to go on the ground. Would be easy enough to just switch to a larger tank and incorporate your idea.

Maybe I’m over analyzing the situation and reacting to essentially a very minor detail, but heck enough minor details can add up.

It's funny how different folks can have opposite experiences. I've done like XJet and for over 40 yrs. I've emptied my left over/overflow back into my main fuel jug. You can count the number of dead sticks I've had in the last ten years on your fingers so it's something more complicated than just the residual fuel causing the problems. I've been flying heli's for over 5 yrs and the only dead stick I've ever had was a glow plug that had NO element left when I got it down. (Yep, that run got pretty lean due to the muff pressure line splitting in flight) I defuel/catch the overflow right back into the main jug on the heli's as well. I can't explain why some have more problems than others with this method but the answer isn't as simple as it might seem as I live in HIGH humidity Houston, TX of all places and have for all 52 yrs of my life. I've flown glow powered planes since I was 6 (my uncle flew control line and got me started). I was very poor growing up and the catching the spillage and pumping the leftovers back into jug (back then it was all cans) was a way to not waste anything. One thing I will venture a "guess" to is it may have to do with how long the fuel sits AFTER it gets moisture in it because once I open a jug it don't hang around long (couple of weeks tops).

Wow, Is in't great that two of us can have toatally different experiences with good results. So Biily Goat, read and make your own choice. Looks like it may not matter much either way.
There are no hard fast rules. .....'cpt maybe rule 4on't fly when the grass is brown.
&
rule 12: don't fly until the temp reaches your age.
other than those 2, go for it.

My experience is that 4-strokes are a bit fussier than 2-strokes regarding fuel contamination. My 2-strokes are happy with the "spit" at the bottom of the fuel jug, but my 4-strokes will object.

Not sure why, maybe others have different results, but that is my experience.

Say your fuel gets moisture in it. What can be done to remove it? Maybe some Heet? I also read somewhere that you can use Heet to blend your own fuel.

I believe the answer is nothing can be done. Once contaiminated with moisture, there is no practical way to remove it from the fuel. Use the fuel to break in a new engine, kill weeds, or take it to the hazardous waste dump.