PEX vs. Copper Repiping in Desert Heat: Which Wins?
We install both. Here is the honest comparison in the specific conditions that matter here: 150-degree attics and water that already killed one copper system.
The short answer
For San Tan Valley conditions, PEX-A with expansion fittings. It cannot pinhole, scale does not bond to it, and it handles attic temperatures well when insulated and UV-shielded. Copper remains a good material — it simply failed in your house for local reasons that would not change if you installed it again.
When a homeowner is repiping, this is the question they research hardest — and most of what they find is written for climates that are nothing like ours. So here is the comparison in the conditions that actually apply: an attic that exceeds 150 degrees in July, and water at 15 to 18 grains per gallon that already ended one copper system.
Head to head
| PEX-A | Type L Copper | |
|---|---|---|
| Resistance to our water chemistry | Immune. No pinholes, no interior corrosion, scale does not bond | Vulnerable to pinholing, especially on the hot side |
| Attic heat | Rated well above summer attic temperatures; must be shielded from UV | Unaffected by heat, but expands and contracts and ticks against framing |
| Joints | Fewer joints per run; expansion fittings, no open flame in an insulated attic | More soldered joints, torch work in a hot confined space |
| Freeze tolerance | Expands somewhat before rupturing | Splits |
| Water hammer and noise | Quieter — the material absorbs surge | Transmits noise; can hammer without arrestors |
| Installation cost | Lower material and labor, smaller access holes, less drywall repair | Higher on both |
| Inner diameter | Slightly smaller per nominal size — we upsize where flow matters | Excellent flow characteristics |
| Service life here | 50+ years with correct installation | 20–40 years depending on water chemistry and pressure |
| Resale perception | Widely accepted and now standard in new construction | Some buyers still perceive copper as premium |
Why copper fails here specifically
Copper is a genuinely good material. It failed in your house for local reasons.
- Water chemistry. Aggressive water gradually erodes the pipe wall from the inside, thinning it until a pinhole opens.
- High static pressure. Portions of this area run high line pressure, which accelerates everything and stresses every joint.
- Velocity erosion at elbows, particularly on hot recirculating lines where water at temperature scours the inside of fittings.
- Attic heat cycling. A 90-degree annual temperature swing works marginal soldered joints loose over two decades.
Notice that none of those conditions change if you repipe in copper. You would be installing the same material into the same environment that consumed the last one.
PEX-A or PEX-B?
Not all PEX is the same, and this distinction matters more than most homeowners realize.
PEX-A uses expansion fittings — the pipe is expanded, the fitting inserted, and the pipe shrinks back around it. The fitting does not restrict the inner diameter, the material has better flexibility and better resistance to kinking, and it is the version we install by default.
PEX-B uses crimp or clamp fittings that insert into the pipe, which slightly restricts flow at each connection. It is a legitimate product and it is less expensive. When you compare repipe quotes, ask which system is being installed — see repipe cost guide.
Installing PEX correctly in an Arizona attic
PEX is only immune to our problems if it is installed properly. What that means here:
- UV protection. PEX degrades with sustained ultraviolet exposure. Any run near an attic vent or a gable opening needs shielding.
- Insulation on hot lines — for efficiency and to prevent condensation issues.
- Correct support spacing. PEX is flexible and sags between supports if it is not hung properly, which creates low points.
- Room for thermal movement at direction changes and terminations.
- Upsizing where flow matters — the slightly smaller inner diameter is a non-issue on a correctly sized system and a real one on a lazy one.
Where we still install copper
- Exposed sections where rigidity and appearance matter — visible risers in a garage or mechanical room.
- Water heater connections, where local requirements or the manufacturer call for it.
- When the homeowner wants it and understands the trade-off. It is your house, and we will do good work in either material.
The recommendation
For nearly every home in San Tan Valley: PEX-A with expansion fittings, run overhead through the attic, properly insulated and UV-shielded, paired with a softener.
It is the material least affected by the exact conditions that ended your original system, it costs less to install, and it leaves the entire system accessible rather than buried in a post-tension slab. Details on our repiping service — and southeast Gilbert homeowners replacing polybutylene face the same choice with the same answer.
PEX-A versus PEX-B, which nobody asks about
Not all PEX is the same, and this distinction matters more than most homeowners realise. PEX-A uses expansion fittings — the pipe is expanded, the fitting inserted, and the pipe shrinks back around it, so the fitting does not restrict the inner diameter. PEX-B uses crimp fittings that insert into the pipe and narrow it at every connection.
Both are legitimate products and PEX-B is cheaper. But when you are comparing three repipe quotes and one is noticeably lower, the fitting system is one of the places that difference lives. It is a fair question to ask directly.
The installation details that actually determine whether PEX lasts here: UV shielding on any run near an attic vent or gable opening, insulation on hot lines, correct support spacing so it does not sag into low points, and room for thermal movement at direction changes. PEX is only immune to our problems if it is installed properly.
The bottom line
Whichever material you choose, install a water softener at the same time. You are replacing a system the water chemistry destroyed — PEX will not corrode, but your new water heater, fixtures and appliances are all still downstream of that same water. And make sure the work is permitted: unpermitted repiping follows you to closing when you sell. See whole-home repiping.
Frequently asked questions
In our conditions it is better. PEX does not pinhole, scale does not bond to it, and it handles attic temperatures well when insulated and UV-shielded correctly. Copper remains a fine material — it simply failed in your house for local reasons that would not change if you installed it again.
PEX-A uses expansion fittings that do not restrict the inner diameter, and the material is more flexible and more kink-resistant. PEX-B uses crimp fittings that insert into the pipe and slightly restrict flow at each connection. Both are legitimate; PEX-A is what we install by default, and it is worth asking which any quote includes.
No. PEX is standard in new construction across Arizona and widely accepted by inspectors, appraisers and buyers. What does affect resale is unpermitted work, so make sure whatever you install is permitted and inspected.
