Flexible corrugated stainless-steel gas tubing — or CSST — has been popular with U.S. plumbing contractors for well over a decade because it’s light and easier to work with than traditional black iron gas pipe. (Unlike black iron, which is rigidly secured to the framing, CSST is minimally attached, allowing it to withstand earthquakes and — in theory — to move laterally when struck by a protruding nail.) But despite its excellent safety record, the tubing has building officials in the north Texas community of Mansfield scratching their heads over at least a dozen incidents in which it’s been punctured by roofing nails.

According to Mansfield building official Paul Coker, the problem first surfaced last spring, after a severe hailstorm led to thousands of roof replacements. Reports of leaking gas lines began coming in, including one in the home of a city-council member; that line was found to have been punctured in four places.

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