Is it customary to run rigid soldered 3/4" copper for gas supply and then "Tee" it and add valves and flex lines?
It is under the slab but looks to be in a conduit pipe for protection.
Thanks for any advice.
Every state is different, but here's what the Massachusetts Gas Code says:
Piping Underground Beneath Buildings: (Section 6.1.6) - Where the installation of gas piping underground beneath buildings is unavoidable, the piping shall be encased in an approved conduit designed to withstand the superimposed loads. The conduit shall extend into a normally usable and accessible portion of the building and, at the point where the conduit terminates in the building, the space between the conduit and the gas piping shall be sealed to prevent the possible entrance of any gas leakage. Where the end sealing is of a type that will retain the full pressure of the pipe, the conduit shall be designed for the same pressure as the pipe. The conduit shall extend 4 inches outside the building, be vented above grade to the outside, and be installed so as to prevent the entrance of water and insects.
Clearly, they're saying the conduit and gas line should be brought up into a utility room ASAP after entering the building. From there, it can then be piped overhead - through the framing - to reach the various appliances.
There's also another section that says ANY underground gas piping shall be at least 18" below grade, which means encasing it in the concrete slab would fail inspection (here in MA). I'd be worried about expansion, contraction and settling of the slab causing leaks that won't be properly sealed off because of the tees underground.
In the "Materials" section, Type L or K copper tubing is allowed (with one proviso), but joints must be brazed, not soldered, with a material having a melting point in excess of 1,000*F. The brazing material shall not contain more than 0.05% phosphorous.
Black iron pipe is really the best way to go (inside the building/above grade); the fittings are approved for concealment behind drywall etc.. The stainless steel flexible tubing (eg - TracPipe or Gas-Tite) is also good, but each appliance would have to have a dedicated line with no branches or tees all the way back to a manifold where the gas first enters the building, and you also have to install strike plates anywhere it stands the possibility of being hit by a nail or screw (from drywall and baseboard trim etc etc.)
Like I said - every state is different, but that's how we do it here.