How to Change a Propane Tank. Changing a propane tank on a gas grill is easier than it looks. Once you become familiar with the parts of a propane tank and the steps involved, you'll be able to change the tank like a pro.
Removing the Tank
Turn the gas supply off by turning the valve screw clockwise. The valve screw is located at the top of the tank.
Determine what type of connection your propane tank has: internal or external. For internal connections the gas line is connected to the tank on the inside of the gas valve. This connection has a hex nut and requires a wrench for connecting and removing. Go to Step 3. For external connections the gas line is connected to the tank on the outside of the gas valve with a Marshall type acme nut. This nut is a large plastic nut with ridges that can be connected and removed by hand. Go to Step 4.
Locate the hex nut that connects the gas line from the grill into the valve opening. Using a wrench, unscrew the hex nut using a clockwise motion.
If your gas line is connected externally with a Marshall type acme nut, you can unscrew the valve connection using your hands. Turn the acme nut in a counter-clockwise motion.
Lift the tank off of the grill platform.
Exchange your old tank for a new tank at a store that provides this service. Most local gas stations and hardware stores offer this exchange. You can refill your old tank at a center that provides propane fuel.
Attaching the New Tank
Place the new or refilled tank on the grill platform with the valve opening facing the grill's gas line.
Connect the gas line to the valve opening, using a counter-clockwise motion if it attaches to the inside of the valve. Use a clockwise motion if you are using the acme nut or an outside attachment.
Test the connection. Apply a professional or homemade (see tip below) soap solution to the valve connection using a small paintbrush. Slowly open the cylinder valve using a half turn. If there are no bubbles, your tank is safely connected.