Abstract: An apparatus for dispensing an amount of fluid is disclosed where the amount of fluid and the pressure thereof is controlled by the height of the fluid relative to the spray mechanism that can dispense the fluid. A reservoir is positioned above the spray mechanism such that a column of fluid constitutes the reservoir of fluid. The height of the fluid reduces upon actuation of the spray mechanism. A controller detects the initial height of fluid and the height of the fluid after the dispensing operation to determine the amount of fluid dispensed. The controller is programmed with a parameter for the amount of fluid to be dispensed. If the determined amount of fluid dispensed is not within the parameters, the controller operates an iterative process to refill the reservoir to an amount such that during subsequent spraying operations, the amount dispensed approaches the parameter amount of fluid.