Air pressure for small bladder tank?

what is the air presure in a small bladder tank? it is just a small tank for a moble home I dont know the size. standard blue tank.
thank you
roger

With your pump off and all pressure released through a faucett, the bladder of the tank should be pressurized at 2 or 3 psi below the pressure setting where the pump normally starts. So if your pump is set to start at 40psi, for example, the bladder end of the tank should first be pressurized at 38psi.