PEX vs Copper

Copper tube material alone runs three to five times the price of PEX per foot, and that is before labor. A copper repipe is a soldered job — every fitting is cleaned, fluxed, heated, and sweated, and in a finished house every joint is a fire watch. A PEX repipe is pulled in long runs with fittings only at the turns, crimped or expanded in seconds.

On a whole-house repipe, that difference is not a rounding error. The same house that quotes one number in PEX can quote nearly double in Type L copper, and most of the gap is labor hours, not pipe.

Type M copper — the thin-wall stuff — saves some material money and is where cheap copper bids come from. It is legal for supply in most places and it is the first pipe to pinhole when the water chemistry turns on it. If you are paying copper labor, pay for Type L.

Copper is rigid, UV-proof, heat-tolerant, and rats do not eat it. That buys it four jobs PEX cannot do.

• Exposed runs. Anything visible — a mechanical room, an unfinished basement ceiling you care about, an outdoor stub — looks better and lasts better in copper.
• The water heater connection. Code commonly forbids PEX within the first 18 inches of a water heater because of the temperature at the outlet. The transition happens in copper.
• Direct burial in some jurisdictions, and any municipality whose code has not caught up with PEX. Check before you buy fittings.
• Anywhere the pipe might see sunlight during or after construction.

A hybrid house is normal: copper at the heater and the exposed bits, PEX everywhere in the walls. Nobody's house is a manifesto.

UV is a genuine weakness. PEX degrades in sunlight — the manufacturers rate it in days of exposure, not years. Pipe stored on a truck rack or left across a framed deck before the drywall goes up is already losing life. Keep it out of the sun and this objection disappears entirely, because pipe inside a wall never sees UV again.

Rodents are a smaller, realer problem than the internet says. Mice chew PEX. They also chew Romex, flex duct, and spray foam, so PEX is not uniquely vulnerable — but a chewed wire arcs and a chewed pipe floods, so the consequence is worse. In a house with an active rodent problem, PEX routing deserves some thought: avoid crawl runs along sills where the tunnels are, and fix the rodent problem regardless, because it is also eating your wiring.

The "PEX makes water taste like plastic" complaint is mostly a new-install story. The first flush of a new system carries manufacturing residue, and it fades within days to weeks. A two-year-old PEX system does not taste like anything.

Copper is rigid, so freezing water has nowhere to go and the pipe splits along a seam. PEX expands. It is not freeze-proof — a hard enough freeze will still burst it, and the fittings are less forgiving than the tube — but it survives freezes that open copper like a zipper.

In a crawlspace in a marginal climate, that is the difference between a cold snap and an insurance claim. It is also why PEX took over the Sun Belt slab-leak repipe market: rerouting through the attic in PEX is faster, cheaper, and more freeze-tolerant than jackhammering the slab to fix copper in the ground.

One caution runs the other way. PEX in an attic in a genuinely cold climate needs insulation discipline, because while the tube survives a freeze better, the crimp fittings and any brass in the run do not share the flexibility.

Repiping a house or roughing a remodel: PEX, pulled in home runs off a manifold if the budget allows, with copper stubs at the heater and anything exposed. Exposed mechanical room, outdoor runs, or a code that says copper: copper, Type L, and not a foot of Type M.

Who should pick all-copper anyway? Someone in a rodent-heavy rural property who cannot solve the mouse problem, someone whose local inspector still flinches at plastic, and anyone who values a fifty-year material over a thirty-year one and is willing to pay double for the sentiment. It is not an irrational choice. It is just an expensive one.