Copper or composite gas pipe: what is used inside a home and why

Internal gas lines are run in one of two materials, and both are fine when fitted correctly. What matters is that the installer uses one of them, fits it properly, and does not substitute something that looks similar.

Copper

The traditional choice. Rigid, long-lasting, joins with compression or brazed fittings, and visibly obvious as a gas line. It needs clipping at regular intervals, sleeving through walls, and protection where it might be knocked. It is more work to bend around a difficult route.

Composite multilayer

A plastic-aluminium-plastic pipe approved for gas. Lighter, bends by hand, faster to run, and does not corrode. It must be the gas-rated version — plumbing multilayer looks identical and is not the same product. Joins are press or compression fittings specific to the system.

What neither should be

• Ordinary PVC or CPVC water pipe
• Garden hose or rubber LPG hose used as a fixed line
• Any pipe run concealed inside a wall without a sleeve
• Any joint buried where it cannot be inspected

Questions for the installer

Which material, and is it gas-rated? How will it be clipped and protected? Where will the isolation valves be? Can I see the pressure test? A good installer answers all four without hesitation.

If an existing line in your home is plastic water pipe or a rubber hose running through a wall, have it inspected. It may have been done years ago by someone who did not know better, and it should be replaced before it fails rather than after.

Longevity

Either material, properly installed, outlasts the appliances it feeds. The failures we see are almost never the pipe — they are joints disturbed by later work, and connectors left past their life.