I just recently fininished my kegerator build with plans to post pictures later. In efforts of avoiding a leak for a leak in the gas line by pressurizing the line and turning off the tank. Both manifolds held pressure when open with no issues. I pressurized the pin lock keg and let it sit for a few hours and that also held pressure without issue. I have replaced both post rubber rings along with the lid rubber ring using food-grade keglube. My CO2 tank was sitting at 800PSI when fully pressurized (It's an old tank I had rehydrotested and filled so i'm assuming it's full) When I connected all the lines and started carbing my first homebrew beer and dropped the fridge from 20 C 5.5 C (~75F->42F) the tank pressure dropped from 800PSI to 550/500 PSI.
No soapy water has shown any bubbles but i'm still concerned. How accurate are the tank pressure gauges (It's a taprite dual body triple gauge regulator) as this one is at the lower limit of green. I'm assuming dropping the temperature and starting to carbonate a keg will drop the pressure of a 20 pound tank however I'm looking for more experienced individuals for reassurance.