A reusable tool assembly for purging fluid from a fluid flow pipe system or a portion thereof is presented. The tool assembly includes an input portion configured to accommodate a positively-pressurized flow of air/gas, a flow control portion configured to regulate an amount of pressurized air/gas flow, and a pressure measurement gauge device configured to measure and indicate the amount of pressurized air/gas flow, as regulated by the flow control portion. The tool further includes and an output portion configured to introduce the regulated amount of pressurized air/gas flow into the fluid flow pipe system, the output portion containing a pressure-fitted slip coupling device that temporarily, releasably, and sealably engages an exterior, unthreaded surface of an open pipe portion providing access into the fluid flow pipe system and enabling the air/gas flow to purge fluid from the fluid flow pipe system.