A system and method for leak testing a thermoplastic piping system is disclosed. The leak test system includes a pump assembly having an air pump configured to pressurize a piping system with air, wherein the air pump is configured by design not to output pressure exceeding the piping system design limitations. The pump assembly further includes a pressure sensor, pressure controller, pressure switch, and solenoid valve for maintaining the pressure within the piping system to a prescribed pressure. The leak test system can include tubing for connecting the pump assembly to the piping system, and further include an ultrasonic leak detection device to locate potential leaks identified on the piping system. As such, the leak test system can safely leak test a thermoplastic piping system, including brittle piping, with low pressure air, while being capable of re-pressurizing the system to compensate for pressure variations therein due to leaks and/or other external factors.