PEX or copper: choosing repipe material in Phoenix

What each one is good at, and where each one fails

This page is about supply repiping done because of leaks — see whole-home repiping for when that conversation is worth having at all. Once it is, the material question comes up immediately, and it deserves a straighter answer than either side usually gets.

Copper

Rigid, long established, indifferent to heat, and it holds its shape, so runs are neat, supported and easy to follow years later. Joints are soldered or pressed, and a properly made joint is not the weak point.

Where it fails: pinholes along the pipe rather than at joints, in certain water and soil conditions; abrasion wherever it moves against a rebar chair, a framing member or another pipe; and — the reason so much of this site exists — it fails quietly under a slab, where nothing tells you for a long time.

PEX

Flexible, so a run can often be pulled through a wall or attic with fewer openings, and with far fewer joints. That last point is the real durability argument: most failures in any system happen at connections, so a run with fewer connections has fewer places to fail. It also tolerates movement, which matters in ground that shifts with the seasons.

Where it fails: at fittings, if the wrong fitting or the wrong technique is used; where rodents or abrasion get at it; where it is left unsupported and sags; and in sunlight. Ultraviolet exposure degrades it, and in Arizona "keep it out of the sun" is not a footnote.

Mixed-material houses, and why transitions matter

The Valley's late-1980s to 1990s stock is where copper meets CPVC and early PEX. Chandler's median home dates to 1997 and Peoria's to 1998, and both sit squarely in that era. Mixed-material houses are the awkward ones: the failure point is often the transition fitting between two materials rather than either run itself.

The practical consequence: if you are putting PEX into a copper house, or repiping part of a house, the transitions between materials are where the attention belongs. A house that is all one material with properly made joints is a simpler thing to own than a house with three materials and six transitions in a wall nobody can see.

Source: U.S. Census Bureau, American Community Survey 5-year estimates (2023)

How to choose, honestly

• If copper keeps pinholing in your house, putting the same material back into the same conditions is a decision worth making deliberately rather than by default.
• If openings have to be kept to a minimum — tile walls, plaster, finished ceilings — the flexibility of PEX is a practical argument, because fewer openings is less to put back.
• If runs will be exposed in a garage, on an exterior wall or across a roof, copper or properly shielded PEX. Bare PEX in Valley sun is a mistake with a timer on it.
• For hot water and recirculation, both are fine. Insulation decides how it performs, not the material.

What should not decide it

Not what a neighbour has, and not a brochure. The pipe that lasts is the one installed with the fewest joints, supported properly, kept out of the sun and protected where it passes through framing. We will tell you what we see in your house and what we would put in it, and then it is your call.