Originally Posted by onthekeg
There is nothing wrong with the tank. If it has only 120 psi it is about empty.
Depending on where you go to get it filled, they might make you get it hydro tested before they will fill it. I think most brew shops just swap them for new ones, so it might not be an issue but some places that actually re-fill them will check the last test date.
And ya, 120 psi is almost empty. The gauge should read 500-800(depending on how cold the tank is) until shortly before you are out of CO2.