Copper vs PEX for Valley Homes

What does California's plumbing code allow besides copper vs PEX?

California's code allows more than copper vs PEX: Table 604.1 of the 2025 California Plumbing Code also lists CPVC, PE-RT, PE-AL-PE, polypropylene, stainless steel, ductile and malleable iron, and ASTM A53 galvanized steel as water distribution materials. PE and PVC are limited to the building supply line or exterior cold water.

PEX came late to California. The BSC's notice for "Adoption of Statewide Regulations Allowing the Use of PEX Tubing" is dated August 16, 2010, covering hot and cold potable water in homes and other buildings. A 2006 Virginia Tech thesis noted that PEX had been banned in parts of California over concern about MTBE leaching, four years before the statewide adoption. One relative is still excluded: PEX-AL-PEX "is not adopted" for potable water in California (Table 604.1, note 5).

How do copper and PEX handle earthquakes?

No code rule or study this site found picks copper or PEX for earthquake performance; the rules focus on connections and shutoffs. In the 1994 Northridge earthquake, LADWP counted about 1,400 leaks in its own system, according to NIST's fire report, but that count covers utility mains, not house piping by material.

What the state does stress is flexibility at the water heater. The Division of the State Architect's older bracing guideline (2014) "strongly recommend[s]" flexible connectors on the water and gas lines. The 2025 code limits copper or stainless flexible connectors to 24 inches and keeps PEX out of the first 18 inches off the heater (§604.13). Pipe supports, two water heater straps and a main shutoff you can close matter whichever pipe you choose; the quake folder covers each.

Does chloramine affect copper vs PEX?

Chloramine's effect on either pipe is not settled in the sources this site could find. LADWP, Burbank and Glendale disinfect with chloramine; LADWP's 2025 water quality report lists a total chlorine residual of 1.7 mg/L on average (1.4-2), against a 4 mg/L limit.

For PEX, the test that exists is for chlorine. Uponor's FAQ says "all PEX manufacturers are required to test their pipe's resistance to hot, chlorinated water" and to print the PEX designation on the pipe, so read the print line on the tubing before it goes in. No chloramine-specific rating was found.

For copper, the 2006 Virginia Tech review of pinhole-leak research (Farooqi, Table 5) lists chloramine's effect on copper pitting as "not known." Copper at the tap stays well under the federal action level in LADWP's 2023 sampling (529 ppb at the 90th percentile), while Glendale's 2025 report shows 760 ppb with 3 of 51 sites over the 1,300 ppb action level. The chloramine page explains the disinfectant itself.

Which lasts longer, copper or PEX?

No primary source gives a service life in years for either pipe in Valley water, so this site does not print one. LADWP's FAQ, comparing copper with galvanized steel, says copper pipes "last longer and generally do not significantly affect water quality as they age." Uponor says its PEX systems "last the life of the structure," a maker's claim.

What shortens either pipe's life is better documented. Failure reports reviewed by Virginia Tech link copper erosion corrosion to pressure over 80 psi, flow faster than 4 to 5 feet per second, and hot water above 160°F. LADWP adds that copper corrosion can come from electrical grounding to water pipes and from hot-water recirculating systems that are undersized or pumped too fast. Keeping house pressure at or under 80 psi, as §608.2 requires, protects both materials; see the pinhole leak page.

What are PEX's weak points?

PEX's main weak points are sunlight, heat at the water heater and solvents in soil. Uponor rates its white tubing for one month of UV exposure and its red and blue tubing for six months, so PEX should not be left in the sun on a job site or run exposed outdoors.

The code adds its own limits: no PEX within 18 inches of a water heater, PEX in continuously recirculating hot water systems must meet ASTM F876-2015a, and PEX buried for drinking water must be sleeved with material "impermeable to solvents or petroleum products" (Table 604.1, notes 3-4). Copper's own weak point is the pinhole leak, covered on the pinhole page.

Which is easier to install in an existing house?

PEX is usually easier to route through finished walls and attics, because it comes in coils and bends around framing, while copper needs rigid runs joined by solder or press fittings. Both need the same permit, inspection and hot-water insulation (§609.12).

In Los Angeles, a full repipe must also bring hot water to each fixture with no more than 0.6 gallons delivered first (LAMC 94.610.4.1.1), so routing and pipe size count for either material. The repiping page walks through permits and contracts.