I kegged my first two batches today and I am having some trouble with my CO2 tank. When I got it filled earlier today the high pressure gauge read 200 psi when I connected it. I've had two kegs carbing at 30 psi for a couple hours now and it is now reading 100 psi. I could not detect any leaks, but like I said, I am new to kegging. Is my gague just not working? Is there some way I can tell how much CO2 left. Even with a leak, there should be more than 100 psi left right? Need some help.