A quick tutorial of how to perform a decay test. Close off the core removal tool to isolate the system and watch for a rise in pressure. On a small system like this (9k btu) a few minutes should be good. On larger systems you'll want a longer decay. If the pressure spikes and doesn't flatten, it's most likely a leak, if its rises and flattens at 2000 microns for instance, you have some more evacuation to do. This set up had the system down below 500 microns in less than 5 minutes. Tools used in