Water company not only wants an air gap but the water has to overflow out of the drinker before it gets to the inlet level.Not a lot, I would be inclined to just make a portable isolator (air gap to prevent siphoning) for the line, and use one
or make a trough from a barrel like on Russ' video I linked, but put the valve above the water level and kink the float arm downwards
Had to cut the side down on some concrete drinkers to pass inspection