Converting a propane gas log to one that operates on natural gas can be accomplished with a suitable conversion kit. Select a kit that works specifically with gas logs to ensure you obtain the correct fittings, and the regulator you need to make the conversion. Switching from propane to natural gas makes sense if your home has recently been hooked up to a natural gas source, allowing you to discontinue using propane for your fireplace needs. The logs themselves don't actually require any modification. It is the regulator unit that must be changed.
Shut off the gas supply leading to the fireplace. This is usually a valve that screws open and shut the same way a garden hose is turned on or off. In addition; shut off the propane fuel supply leading from the tank.
Remove the regulator from the fuel supply line by loosening the fittings with an adjustable wrench. Regulators unscrew from the fuel supply lines easily, once they are loose. Remove the fuel line leading to the gas logs from the propane fuel regulator.
Apply thread sealing tape to the threads of an adapter from the kit, then thread it into the fuel supply line. Thread the body of the natural gas regulator over the threads of the adapter, again using thread sealing tape on the adapter threads.
Apply thread sealing tape to the second adapter from the kit, and fasten this adapter to the line leading to the gas logs. When this is done, apply thread sealing tape to the other end of the threads of the adapter, and thread it into the open end of the natural gas regulator.
Tighten all the fittings you installed, then turn on the fuel supply. You hear an initial hissing sound as the lines fill with natural gas. If you detect the smell of natural gas, shut off the gas supply and double check all the gas fittings before attempting to use the fireplace.