i don't make this stuff up these are just basic fluid facts.

i didn't want to confuse anyone even further but the back pressure is actually to an extent canceled by the height of the liquid in the return tube,

as an example i'm sure people can understand that if the tube was only 1" higher than the level in the tank and you poured fuel into the tube then stopped the level in the tube would be the same as the level in the tank so in reality with regards to level there is no backpressure.

fluids exert pressure in all directions.