I want to install a new natural gas line in my backyard to supply a new, built-in fire pit.

I'm located in Huntington Bach, CA.

I currently have a BBQ island with a gas supply line from the meter directly to the island, approximately 75 feet. A stub out was provided on the side of the island for future use.

I want to install a new gas line to supply the fire pit, approximately 25 feet from the BBQ island. I have dug a trench 18" deep for the line to run from the stub out to the fire pit. I have decided to use a manual, key operated gas valve and stainless H-shaped burner for the fire pit.

What supply line materials, fittings, and valves should I use for this installation? I have read about yellow polyethylene piping (needs tracer wire), CSST piping (although it says must be protected if buried), and plain black iron covered in tape. I have read that the polyethylene fittings are quite expensive, but I'be been told to expect a materials price of $100-150 for the job.

I'd also like to add a timer to the valve.

Can any plumbers or experienced DIYers offer some advice?

Thanks,
Aaron