Plumbing Pipe Materials and How They Differ

Copper

Long established, rigid, and tolerant of heat, which is why it still appears on water heater connections even in houses piped in something else. It corrodes over decades depending on water chemistry, and it is the material most likely to develop pinhole leaks where water is aggressive. It is also the most expensive to install, because every joint takes time.

PEX

Flexible, quick to run, and more freeze tolerant than rigid pipe, because it can expand slightly before it splits. That matters in Idaho. It runs in long continuous lengths with fewer joints, and fewer joints means fewer places to leak. It should not be exposed to sunlight, and the fitting system used matters more than the pipe itself.

PVC and ABS

Drain, waste and vent work rather than supply. Not for hot water under pressure. Failures are usually at joints or from physical damage rather than the material giving up.

Galvanized steel

Found in older housing stock. Steel pipe with a zinc coating that eventually wears through, after which the pipe corrodes from the inside. The internal diameter narrows with scale and rust, so the symptom is falling pressure everywhere at once, and discoloured water on first draw. Galvanized supply lines are the most common reason a whole-house repipe gets quoted.

Polybutylene

Grey plastic pipe used widely in the 1980s and into the 1990s, then withdrawn. It becomes brittle and fails, frequently at fittings and frequently without warning. If a house has polybutylene supply lines, the question is when it gets replaced, not whether.

Why it matters to you

The material decides the failure mode. Galvanized fails slowly and visibly, as pressure loss over years. Polybutylene fails suddenly. Copper can develop pinholes. PEX is most often damaged rather than degraded.

Knowing what is in your walls tells you which of those to expect, and whether a repipe is a maintenance decision or an urgent one.