Laying the pipe run is the bulk of the cost. I doubt you'd pass inspection on an already buried pipe as well. Tell her to get a quote to have the pipe run and get a rough inspection. It's probably not as high as she's thinking.
18" here IIRC.Your already digging, plastic pipe 12" down with a tracer wire.
Don't need slope for a gas line. It's pressurized. :blink:Bury empty conduit, with long sweeps, through which plastic pipe could later be run. Talk to a plumber first - you need slope and probably other complications.
I'm not sure if you were joking.Don't need slope for a gas line. It's pressurized. :blink: