A powder supply system for a powder-coating installation, especially a parts painting installation using electrostatic powder, according to the invention, comprises a tank designed to contain the powder, means for feeding powder into the tank, means for injecting compressed air into the bottom of the tank in order to fluidize the powder, and an exit pipe in which the powder is entrained by the air from the tank, this pipe being connected to at least one powder using device situated at a distance, in particular a spray gun. The system also includes means for reducing the pressure in the tank below that of the feed means in order to fill the tank with powder.