See if the city will verify the install with their engineering staff if you get a permit. You can probably draw up a sketch, size your runs and then ask if you can get an engineer to review prior to installing. Also gets you clear of the possible insurance issues.

No nut unions are allowed, but you can easily plumb into a line by replacing an existing elbow with a T. Run the new flexible type line. I had a line added for a dryer 10 years ago, the plumber did just that. Picked an existing elbow and ran back a flex line for the dryer about 6 feet. Afterwards I thought, I could have done that!