Can you use PVC, CPVC or PEX water pipe outdoors in Phoenix?

Phoenix amends both plumbing codes it adopts. The IPC amendment, 605.25, and the UPC amendment, 604.14, say the same thing: "Non-Metallic potable water pipe, fittings, and valves shall not be exposed in exterior outdoor locations." The next sentence completes it: "Components of the exterior exposed potable water system shall be metallic only." The approved metals are the ones listed in IPC Tables 605.3 to 605.6, or UPC Table 604.1 for the UPC.

The amendment's own justification gives the reason: nonmetallic pipe, fittings and valves would be "subjected to extreme exterior heat and will soften and sag between pipe supports," and the sun's UV rays "will cause the pipe to become brittle and be subjected to fracture and breakage." It names the locations of concern as "areas of direct sunlight, such as roofs, ground surfaces, and exterior wall locations." The city marks the IPC version, 605.25, as carried over from an earlier code cycle, and the UPC version, 604.14, as new. Both are part of the 2024 code that Ordinance G-7397 put in force on August 1, 2025.

• Nonmetallic pipe: plastic water piping such as PVC, CPVC and PEX, and plastic fittings and valves.
• Exposed: in the open outdoors, not covered. A pipe in direct sunlight on a roof, along the ground or on an outside wall is the target of the rule.
• Potable: drinking-quality water piping, meaning the domestic supply.

Anyone installing or replacing exposed potable water pipe outside a building in Phoenix: rooftop water lines to equipment, supply lines along exterior walls, piping at grade near a meter or backflow assembly, and the fittings and valves on those lines. It applies whether the design follows the IPC or the UPC.

• A restaurant adds a rooftop water line for equipment. The line is exposed to direct sun, so it has to be metal, with metal fittings and valves.
• A landlord repairs an exterior supply line along a wall with a plastic coupling. The rule covers fittings as well as pipe. A plastic coupling on an exposed outdoor line does not meet it.
• The same line runs inside a mechanical room. The answer flips: the amendment addresses exterior exposed locations, not piping inside the building.
• An irrigation line is plastic. The amendment is written for potable water. Whether a particular landscape line counts as potable depends on how it is connected, so check with Planning and Development before you rely on that.

The city's reasoning is practical. In the city's words, exterior summer weather is extreme, and plastic pipe exposed to that heat softens and sags between supports. The city also names UV as a hazard: sunlight makes the pipe brittle, so a strain that a fresh pipe would take can crack an aged one. Both failures end in the same place, a water break and property damage. The IPC amendment's cost note says the extra initial cost is offset by fewer of those breaks and less liability.

1. 1Walk the job and mark every exposed outdoor potable-water run: roofs, exterior walls and grade, including shaded locations.
2. 2Specify metal pipe, fittings and valves for those runs from the approved metal tables in the code.
3. 3If an existing plastic line is exposed, consider replacing the exposed section when you do other work on it. That is our suggestion. The amendment says nothing about existing lines.
4. 4Put the materials on the plumbing permit plans, and ask Planning and Development if you are unsure about a location.

• "Insulation or paint makes plastic legal outdoors." The amendment sets no such exception. It says exposed outdoor potable components are metallic only.
• "Only the pipe is covered." The text names pipe, fittings and valves.
• "This is the national plumbing code." It is a Phoenix amendment. Mesa and Scottsdale have no matching local rule, so a contractor working in several cities has to check each one.