Bob and Tim are on air-conditioning system service call, and the system has a persistent leak. It seems to leak down about once a month and has to be recharged. Several technicians have tried working on the system and cannot seem to find and stop the persistent leaking. Their service order says to says to repair the leak using whatever methods needed to be used. This persistent leak must be stopped.
They arrive at the job and look the system over and discover that it is truly low on refrigerant again.