the pressure in the hose 6 is essentially equal to the pressure in the tank 5 because the float valve assembly 14 15 16 and the exit tube 11 offer little or no resistance to flow while the flow restrictor 28b at the downstream end of the hose 6 offers significant resistance to flow the pressure in tank 27 is maintained at a lower pressure and therefore there is flow through the restrictor 28b the vapor or gas flows continuously to the vacuum tank 27 the compressor 24 then provides the motive power to move the vapor or gas intermittently from the tank 27 and to keep its pressure significantly below the pressure in the tank 5 when the liquid level rises to the maximum value 8 and the float 15 seals against the seat 16 the supply of vapor or gas to the hose 6 is cut off and the pressure in hose 6 drops precipitously the drop in pressure is sensed by the pressure sensor 21 the pressure information is conveyed via the control wiring 34 to the microprocessor 30 and the microprocessor immediately stops the fill the sensor 21 can also be a flow meter the reduced flow of vapor or gas into the hose 6 can be sensed by a change.