Galvanized Pipe

Galvanized pipe is carbon steel tubing dipped in molten zinc to create a protective coating that slows rust and corrosion. The zinc layer reacts with water and air to form a carbonate scale that seals the surface. In the field, it's recognizable by its dull gray-silver finish and the characteristic rough texture.

Galvanized was the default for potable water lines and gas service from the early 1900s through the 1980s. It lasted reasonably well in dry climates and neutral pH water, but in acidic water or areas with aggressive water chemistry, the zinc coating deteriorates and the steel underneath rusts. The interior corrodes over time, restricting flow and releasing orange-tinted water. The zinc itself can leach into water at higher temperatures, which became a code concern.

Today, you pull it out on old repiping jobs, replace it with copper or PEX, and deal with seized fittings and brittle pipe that cracks under the cutter. Some jurisdictions still permit galvanized for non-potable uses like gas vents, but it's essentially obsolete for new water supply work. Know how to unscrew it without destroying the next section and when a dielectric union is required between galvanized and copper.