I recently had my house undergo an inspection in process of a sale.

The only thing that the inspector pointed out was that the gas line from my furnace to the water heater in utility closet was copper. That was not standard practice now days and should be looked into.

We do have an old house with a 19 year furnace. I plan on calling a licensed plumbing and heating company but wanted some feedback as to in today's setup what is the material of the pipe that should be used.

Regards Sid

  • There are a lot of things that are not standard but there is absolutely no problem with the install. I have seen many inspections that had all kinds of write ups and not a single one was valid! To provide an example of one that ended up in court a 1897 home with knob and tube and cartridge fuses for mains and Edison screw in glass fuses for branch circuits. This idiot said it was a requirement to update the wiring! Luckily they called me as I was doing electrical in that area to maintain historical tax exemption! If they would have changed the wiring they would have lost it.
    – Ed Beal
    Jun 29 at 21:57
  • 1
    The National Fuel Gas Code (NFPA 54/ANSI Z223.1) and all of the major model building codes have approved copper for the use in fuel gas systems. In fact, in states like Minnesota, Alabama, Georgia, Florida, etc, copper is the dominant, if not the primary choice, for flexible fuel gas piping systems in homes and multi-family units. IAPMO approved copper for use with fuel gas in 1999. Found this on the web, It may not be normal in your area I have used ACR copper for propane, acr is high pressure compared to water pipe. What should be used is opinion.
    – Ed Beal
    Jun 29 at 22:04
  • Do you have any local amendments to the NFGC or IFGC that prohibit the use of copper? As Ed said, the NFGC permits it provided the gas is "sweet" (below a certain sulfur content); the IFGC is the same way, and the house I live in has a copper line feeding the water heater that's been in service for quite a few years now with no issue Jun 29 at 23:18
  • I'm confused, why is your furnace providing gas to your water heater? Each appliance should be getting supplied from the trunk or branch. You should consider adding a picture. From everything I've found copper is not code-compliant for natural gas nowadays but if it's an existing installation and not leaking/corroded then you don't have to do anything.
    – MonkeyZeus
    Jun 30 at 16:38

Gas lines today (in my area at least) are typically CSST (Corrugated Stainless Steel Tubing) which is flexible and coated in a yellow rubber jacket, it has threaded connectors on each end which makes it easy to install. My home has a manifold for distributing gas to the water heater, furnace, and a gas fireplace but all the piping is CSST.

Previously most gas lines were black iron pipe, and while this can still be found in many older homes it isn't as common in new construction. Since you're replacing, CSST would probably be an appropriate choice (ask your plumber).

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