What is the interior diameter of the connecting hose?

A water level is a hose, with water, and a vertical guage at each end
of the hose, used for leveling or determining the level of a surface.
I have one 75' long, with a hose of 1/2" interior diameter hose.

Your connecting hose can not have an interior diameter of 3/8" or
less, or, like a water level, it will not work properly by leveling
itself off. Air pockets are most likely to get trapped and affect a
water level when using a tube or hose of 3/8" or less (in interior
diameter), also, and that is why water level hoses must have an
interior diameter of greater than 3/8". Osmotic pressure!!!

Sonny