Originally Posted by jones2r
Any float-level system will not be linear unless the tank is square-dimensioned (not necessarily square-shaped). This doesn't mean that the float gauge won't be useful, just not gauge-accurate. You will have to employ Kentucky calibration (bastardization of a shooting term, Kentucky windage). What would be useful in this case would be to fill your empty tank with a known quantity of liquid, and mark your gauge's face accordingly.
They make floaters that have different height shafts because of that.
I know I have 3, all different size. The gages only say full, half etc.
If he knows the quantity of water it takes, then its easy to calculate the quantity indicated.
Also most of them, can be calibrated for float travel, ie what is marked with float all down and all up.