I have a cottage in Connecticut that is gutted and being re-built. It is on a slab. There are 2" x 4" studs (stringers) lying flat over plastic on the cement floor. I wanted to install conduit now, along a stringer, that will be under the not yet installed plywood and oak flooring. This would be for future installation of an LP line, for a propane fireplace. There is a 1 1/2 inch clearance between the cement and the flooring. If I put a 1 1/2" sleeve, will that be large enough to run a LP line through, and what is the best type of material to use ? Thank you

  • Why not install the pipe now, and cap it on both ends? – Mike Baranczak Oct 10 '15 at 21:12
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    I believe that 2x4s lying flat like that are called "sleepers", not "stringers", yes? – Jimmy Fix-it Oct 11 '15 at 21:21
  • Correct, they are called sleepers. – Jack Oct 18 '15 at 1:39
  • Will it be accessible? You should always be able to access your propane lines. Also I always run everything in schedule 40 black Iron for propane it is way better volume and more rigid – A.farrow Feb 5 '17 at 22:01

The bigger concern in regards to running any metal conduit (but especially pressurized gas filled) close to concrete floors is taking proper precautions to keep the metal from making contact. If the two dissimilar materials remain in contact over time the alkaline in the concrete will corrode the metal possibly to failure. To ensure this degradation doesn't occur standard practice is to wrap the pipe with a HD 6 mil thick pipe wrap tape. You can also purchase black gas pipe that is already coated with a yellow protective skin. This would be the minimum to pass code, but I would install the pipe above code for your own well being. I'm guessing you will be limited to using 1/2 inch pipe due to the 1 1/2 inch floor sleepers (tip O' the hat to @Jimmy Fix-it). Finding a spacer thin enough to separate the pipe and floor could be challenging. Possibly a rubber material/ sheet?


Is that the only thing that will run on propane?

The amount of other appliances and length of run determine pipe diameter.

I have propane in my place and it starts with 1" outside the house @10 PSI, then it hooks to a regulator that goes down to 3/4" Corrugated stainless steel (CSST) and 1/2 PSI. Then from there it branches out to all my appliances in 1/2" CSST by means of connectors that allow the branching off to other sizes. That does not mean it will work with what you need, these systems are usually designed, but you could prep for the largest possible diameter...

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