Before you even look at the old tank, close the main valve. You know, the big wheel on top? Turn it clockwise until it stops. This is non-negotiable. Do not skip this step, unless you enjoy the sound of pressurised gas escaping at the speed of sound and the cold burn of frostbite on your fingers.
I’m serious—I once forgot to close the valve on a 20-pound tank, and the resulting mist cloud looked like a magical entrance to Narnia, but cold. And loud. And expensive. Close the valve. Your wallet will thank you.
