How long old pipes last before they fail depends on the material, so treat every number as a range. One published chart puts copper water lines at 50 to 70 years, cast iron drains at 50 to 60, PEX near 40, and PVC or ABS drains at 50 to 80. Water, soil and installation move the date.
The ranges, material by material
The best-known public table of home component lifespans is InterNACHI's life expectancy chart. InterNACHI is the home inspectors' trade association, so it is a fair benchmark, but read it as a rule of thumb. Even inside that one chart, copper water lines show up at 70 years in one row and 50 in another. That gap is the honest picture: a range, not a date.
| Material | Typical range | What usually ends it | Deeper page |
|---|---|---|---|
| Copper water pipe | 50 to 70 years (InterNACHI lists both) | Pinhole leaks from pitting, thinning at joints | Pinhole leaks in copper |
| Galvanized steel water pipe | Decades; see the linked page for the timeline | Rust from the inside, scale, low pressure | Galvanized pipe problems |
| Cast iron drain pipe | 60 years above ground, 50 to 60 below | Interior corrosion, cracked or scaled walls | Cast iron drain lifespan |
| PEX water pipe | About 40 years in the chart | Chlorine and heat stress, sun on exposed runs, fitting failures | PEX vs CPVC |
| CPVC water pipe | No firm public number | Cracking, especially at joints | PEX vs CPVC |
| PVC and ABS drain pipe | 50 to 80 years | Cracks from ground movement, heat and sun exposure | covered below |
| Polybutylene supply pipe | No safe number | Degrades from the inside and ruptures without warning | Polybutylene pipes |
| Clay or Orangeburg sewer pipe | Old sewer lines, often past service life | Root intrusion, collapse, deformation | What is Orangeburg pipe |
| Brass valves and fittings | No published number | Wear at seals and stems | covered below |
Every number in that table comes with a caveat. The PEX figure of 40 years is a published inspection guideline, not a measured failure date for your house. It is also a different kind of estimate from a laboratory test. The Plastics Pipe Institute (PPI), the plastic pipe trade body, says the product standards for PEX "require that PEX pipe and tubing intended for use in the transport of potable water have a minimum extrapolated time-to-failure of fifty (50) years" when tested under ASTM F2023, at lab conditions of 140 degrees Fahrenheit and 80 psig. That is a test result under fixed conditions. It is not a promise about your wall.
Cast iron shows the reverse problem. The Cast Iron Soil Pipe Institute (CISPI) reports that more than 535 water and gas utilities in the United States have cast iron distribution mains with continuous service records of more than 100 years. So the metal can last a very long time. In a house, drain pipe gets judged by its inside surface, not by the age of the iron. Our cast iron page covers how to tell.
Brass gets no number here because we did not find a source we trust for one. Valves wear where they move, so a shutoff that will not close or weeps at the stem is the sign that matters, not the calendar.
What moves a pipe toward the short end
Three homes with the same pipe can have three different lifespans. These are the factors that account for most of the spread.
### Water chemistry
Phoenix water is hard. The city's 2025 water quality report lists total hardness of 172 to 302 ppm (10 to 17.6 grains per gallon) and a pH range of 6.6 to 8.8. It also says "Hard water can cause some types of scaling in pipes and water heaters" and on fixtures. Our hard water page covers what that does inside a house.
For copper specifically, the CDA handbook lists the usual causes when corrosion problems do occur: aggressive hard well waters that cause pitting, soft acidic waters that block a protective film, excessive water velocity or turbulence, poor workmanship, excessive or aggressive flux, and aggressive soil. Only some of those are about the water itself. The rest are about how the system was built.
### Pressure, velocity and temperature
CDA lists excessive flow velocity or turbulence among its causes of copper corrosion trouble, and that is a design and pressure matter you can influence. For PEX, the cited 50-year extrapolation uses chlorine-aging end-use conditions of 140°F and 80 psig. Those are not universal hydrostatic maxima: PPI distinguishes typical pressure-temperature ratings such as 160 psi at 73°F and 100 psi at 180°F. Water chemistry and recirculation suitability need separate manufacturer checks, and local pressure rules still apply. Keeping pressure regulated and the water heater set sensibly is cheap insurance. See what home water pressure should be and signs a pressure regulator is going bad.
### Soil movement
Buried water and drain lines face the ground. The Arizona Geological Survey says that adding a little water to expansive smectite clay, during a monsoon storm for example, makes it swell "to many times its original volume," and that the clay shrinks when the water leaves in the hot, dry summer. In its words: "The resulting changes in soil volume can cause considerable damages to homes, sidewalks, pipelines, and streets." Pipes under slabs and drains in clay yards move with that soil, and rigid old pipe can crack where it flexes. See signs of a slab leak.
### Sun and heat
Plastic pipe and Phoenix sun do not mix. The city's amendment to the 2024 Uniform Plumbing Code says non-metallic potable water pipe, fittings and valves shall not be exposed in exterior outdoor locations. Its stated reason: "exposure to UV rays from the sun will cause the pipe to become brittle and be subjected to fracture and breakage when placed under stress or strain." Keep that in mind for any plastic stub left in the sun. See also whether Arizona heat damages pipes.
### Installation quality
A pipe installed with sharp turns, no expansion room, bad solder joints or the wrong fittings starts its clock damaged. This is the least visible factor and often the most decisive. Workmanship can change how long a system remains serviceable.
How to read your own house
Start with what you know.
- 1Find the material. Look at exposed pipe near the water heater, under sinks, and in the garage. Copper is brown or green. Galvanized is dull gray with threaded joints. PEX is red, blue or white plastic. Our page on how to find where water pipes run helps.
- 2Note the age. Age and material together tell you where you are on the range. A copper system in the middle of its range needs watching. One at the end of it needs a plan.
- 3Watch for warning signs. Discolored water, dropping pressure, repeat leaks and green crust are the tells. Signs of old failing pipes has the full list.
- 4Look inside if you need to. For drains and buried sewer lines, a camera inspection shows condition without digging. If you are buying an older home, our page on what a plumbing inspection covers when buying sets expectations.
Wait, watch or replace
Here is the simple version.
- Middle of the range, no symptoms: keep the pressure and water heater temperature in check and revisit in a few years.
- End of the range, or one leak: one pinhole in old copper can be a one-off. Several in a year points to a repipe. Ask what is causing them before you pay to replace them.
- Known bad material (polybutylene, Orangeburg, failing galvanized): plan the replacement now, on your schedule, before a leak forces it on the plumber's.
Whichever way it goes, you should get a written price before any work starts. HQ Plumbing & Air is licensed and insured, gives free estimates, and quotes up front, and we will say so plainly if the pipe you have still has years left.