Liquid supply system

An electrostatic spray system (10) includes a supply module (14) configured to store a supply of charged liquid for spraying by an electrostatic sprayer (26). A feed module (12) is connected to the supply module to fill the supply tank (44) of the supply module as needed during spraying to provide a continuous supply of liquid for the electrostatic sprayer. The feed module is controlled such that the feed module is electrically isolated from a main reservoir (18) connected to earth ground potential when the feed module is providing liquid to the supply module, and the feed module is electrically isolated from the supply module when the feed module is receiving liquid from the main reservoir. The feed module transfers the liquid from the main reservoir to the supply module without electrically connecting the supply module to the main reservoir (18).