My house is on a slab. When I purchased the house the first floor ceiling was drop ceiling. I sheet rocked all the ceilings and recently I was told the propane supply line, which is the flexible copper type is not up to code, and I need to replace it. I want to use black pipe, running it from the outside, in my first floor ceiling, into my furnace room (about 15 feet). To make the job easier I want to use a larger section of plastic pipe as a "raceway" since it would be much easier to handle during the process of pushing it through the ceiling, parallel to the floor joists. After the plastic pipe is installed it would be very easy to push black pipe (one contiguous piece) through. Is this allowed? Thanks.