Well the bottom line is that is not deep enough. Check out this chart:
If you only go to 28 in/hg you can see there could still be moisture in the system as long as the air temperature is under 86degF. What’s more important, is that this chart shows you that reading vacuum levels with a bourdon tube type gauge is not accurate enough. You need a gauge that reads microns. Either a thermistor or transducer type device.