PEX vs Copper Pipe: A Fair Comparison for Homeowners

Choosing between PEX and copper for supply lines affects cost, installation and what happens in a freeze. The one source we reviewed is PEX Universe, a vendor that sells PEX but states it does not advocate either material, so its figures are its own claims.

Comparison from that source

Freezing: PEX expands and contracts and is described as more burst-resistant. Rigid copper is rated highly prone to bursting.
Sunlight: PEX is not for outdoor use except underground. Copper tolerates sunlight.
Cost: The page, a PEX seller, says copper averages 4 to 6 times the price of PEX tubing for 1/2, 3/4 and 1 inch sizes (the seller's own comparison of products it sells against Type L copper).
Installation: Copper needs soldering skill and takes longer. PEX is described as easy to install and can run long distances without couplings.
Fittings: PEX needs fewer fittings. The page notes brass PEX fittings may dezincify, though most are now DZR brass or plastic.
Lifespan: The page gives 20 to 50 years for both. One PEX product is cited at a 50-year mean life under ASTM F2023 conditions.

Water chemistry

The page says water quality is the most important factor. For copper it gives an optimal pH of 6.5 to 7.6 and warns that low pH dissolves copper and over-chlorinated water is a problem. For PEX it gives pH above 6.0 and chlorine below 4.0 ppm. Test your water, or request your utility's report, before deciding. Not verified: that these thresholds apply to your products; follow the manufacturer's data.

Code and approvals

We have not verified which pipe your local plumbing code allows, or whether permits are needed. Ask your building department. Not verified: local code acceptance.

Questions for a plumber

Which materials are approved here, and what do you recommend for my water?
What fitting system and warranty do you use?
How will outdoor or sunlit runs be handled?

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General information only. Not electrical, plumbing, legal or code advice. Confirm details with a licensed professional and your local authority.