Patent ID: 7343250

Claim:
A method of calculating chemical usage of a supply tank comprising: providing a chemical system comprising: a first supply tank of known capacity, the tank mounted upon an electronic scale, the scale being capable of generating a series of signals related to the weight of the tank when empty and at various levels of fill; and a system controller for receiving the series of signals from the scale relating to the weight of the tank when empty and at various levels of fill; filling the first supply tank from a source of chemical feed; feeding chemical from the first supply tank to a water system, wherein chemical usage is calculated by inputting into the system controller the series of signal related to the weight of the first supply tank when empty and at various levels of fill to obtain a chemical feed rate; refilling the first supply tank from the source of chemical feed; calculating a projected chemical usage during refilling of the first supply tank by: obtaining a fill time for the refilling of the first supply tank; and calculating the projected chemical usage during refilling based on the chemical feed rate times the fill time; and calculating a total usage of chemical over a defined variable period of time by adding the projected chemical usage during refilling to chemical usage calculated by the system controller.