Method of controlling the flow rate of the liquid by controlling operation of the pump

A method of controlling the flow rate of a liquid from a liquid source to a use location where the liquid is expended, comprising the steps of:

• (a) establishing a desired set point flow rate for the liquid from the source;
• (b) pumping said liquid from said source towards said use location using a powered pump, and determining the flow rate of the pumped liquid from said pump;
• (c) controlling the operation of said powered pump using a controller device to pump the liquid at a flow rate at or about said set point flow rate, by periodically comparing said determined flow rate of the liquid from said source with said set point flow rate, and:
• (i) if the difference between said determined flow rate and the set point flow rate is at or above a first predetermined magnitude, operating said pump so as to alter the operation of the pump at a relatively high aggressive first correction rate, so that said determined flow rate approaches said set point flow rate at the aggressive first correction rate;
• (ii) if the difference between said determined flow rate and the set point flow rate is at or above a second predetermined magnitude but below said first predetermined magnitude, operating said pump so as to alter the operation of the pump at a relatively low moderate second correction rate lower than said first correction rate, so that the determined flow rate approaches said set point flow rate at the moderate second correction rate;
• and
• (iii) continuing said controlling steps (c)(i) and (c)(ii) throughout the flow of liquid from said liquid source.