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.