Picture of a slip in gas fire place.
Step 1: Before you go and get your permit ensure you know where you want to put the fireplace and especially the flue, or vent. Next determine how much pipe and fittings you need. Get Teflon tape or paste and having an extra fitting or two won’t hurt anyone. Depending where you buy the material you can take it back. Plumbing supplies shops charge a 20% restocking fee but their prices are better for bulk piping purchases to licensed plumbers.
Step 2: Tap into your gas line and run your gas pipe to your fireplace. Normally a 1/2 inch line. Remember you cannot have concealed unions. You most probably will have to put a union in and you might have to thread the pipe in place where you cut it at. Run the line to the fireplace right before you make your last connections insure you put the piping system to a pressure test and wait for the inspector to check before you go any further.
Step 3; After you get the gas to the unit make sure you have at least a 6 inch drip leg before you connect to the gas control, with a union and a gas valve all accessible.
Run your flue to the outside and your done. If your doing the rest like making a mantle and bricking around the unit etc. It’s not in this article.
Typical flue on a slide in fireplace.
Flue after completion.