PEX vs Copper Plumbing Fittings: Which Is Right for Your Home?

If you're replumbing a home, adding a bathroom, or replacing old galvanized pipes, you're facing a fundamental choice: PEX or copper? Both are excellent plumbing materials approved by virtually all building codes, but they have very different characteristics, costs, and installation requirements. This guide breaks down everything you need to know to make the right decision.

Overview of PEX Plumbing

PEX (cross-linked polyethylene) is a flexible plastic tubing that has revolutionized residential plumbing since gaining widespread code approval in the 1990s. It now accounts for over 60% of new residential water supply installations in the United States.

Types of PEX (A, B, C)

• PEX-A (Engel method): The most flexible type, made by peroxide cross-linking during extrusion. PEX-A can be expanded and has the best freeze resistance — it can expand up to 3x its size without cracking. It's the premium option and works with expansion fittings. Brands: Uponor (Wirsbo), Rehau.
• PEX-B (Silane method): Cross-linked after extrusion using a moisture-curing process. Slightly stiffer than PEX-A but still very flexible. PEX-B has a slight "coil memory" — it wants to return to its coiled shape. Works with crimp and clamp fittings. Most cost-effective. Brands: Viega, SharkBite.
• PEX-C (E-beam method): Cross-linked by electron beam radiation. The stiffest of the three types, most prone to kinking, and least common. Not recommended for beginners.

For most homeowners, PEX-A or PEX-B are the best choices. PEX-A if you want maximum flexibility and ease of repair; PEX-B for the best value.

PEX Fitting Methods

• Crimp fittings: A copper crimp ring is placed over the PEX where it connects to a brass fitting, then compressed with a crimp tool. The most economical method. Requires a calibrated crimp tool ($30–$60) and go/no-go gauge.
• Clamp (Cinch) fittings: Similar to crimp but uses a stainless steel clamp ring compressed with a ratcheting clamp tool. Slightly easier for tight spaces since the tool only needs access from one side. Same fittings as crimp.
• Expansion fittings: PEX-A only. The tube end is expanded with a special tool, the fitting is inserted, and the PEX shrinks back to create a watertight seal. No metal ring on the outside. The strongest and most reliable connection. Requires an expansion tool ($80–$300).
• Push-fit (SharkBite): Push the PEX onto the fitting and it locks in place. No tools required. Very expensive per fitting ($5–$15 each) but convenient for repairs. Some plumbers distrust push-fit connections for concealed (in-wall) use.

Overview of Copper Plumbing

Copper has been the gold standard in plumbing for over 80 years. It's proven, durable, and universally accepted by building codes.

Rigid vs Flexible Copper

• Rigid copper (Type M, L, K): Comes in straight sticks, typically 10 feet long. Type M is the thinnest wall (most common for residential supply). Type L is thicker (required by some codes and for underground). Type K is the thickest (used for underground and commercial).
• Flexible copper (soft temper): Comes in coils. Used for supply lines to fixtures, ice makers, and humidifiers. Easier to route than rigid but more expensive per foot.

Soldered vs Compression Fittings

• Soldered (sweated): The traditional method. Flux is applied, the fitting is placed on the pipe, and a torch is used to heat the joint while solder is applied. The solder wicks into the joint by capillary action. This creates the strongest, most reliable copper connection. Requires a propane torch, flux, lead-free solder, and practice.
• Compression fittings: A nut and ferrule (olive) compress against the pipe to create a seal. No heat required. Used for exposed connections that may need disassembly (valves, supply lines). Not recommended for concealed joints.

Cost Comparison

This is where PEX wins decisively:

Copper prices fluctuate with commodity markets and have been particularly volatile in recent years. PEX also requires fewer fittings because it bends around corners instead of requiring an elbow at every turn.

Durability and Lifespan

Copper has a proven track record of 50–70+ years. Many homes built in the 1950s still have their original copper plumbing. Copper is naturally antimicrobial, resistant to UV degradation, and doesn't leach chemicals. However, copper can develop pinhole leaks from aggressive water chemistry (low pH, high chloride content) and is susceptible to electrolysis when in contact with other metals.

PEX is rated for a 50-year lifespan, and early installations from the 1980s in Europe are still performing well. PEX is immune to corrosion and electrolysis. It's also more resistant to freezing — PEX can expand without bursting in most freeze scenarios, while copper will split. PEX's main vulnerability is UV light — it degrades when exposed to sunlight and must not be used outdoors or in exposed locations.

Installation Difficulty

PEX is dramatically easier to install for DIYers. It cuts with a simple PEX cutter, bends around corners without fittings, and requires no heat or flames. Crimp and clamp connections take seconds. A homeowner with basic skills can replumb a bathroom in a day.

Copper requires soldering skills, which take practice to develop. A poor solder joint will leak. You need a propane torch (fire risk in wall cavities), flux, solder, and must be careful with nearby combustible materials. Cutting requires a tube cutter and deburring tool. Copper is also significantly heavier and more rigid, making routing through walls more difficult.

Building Code Considerations

Both PEX and copper are accepted by the International Plumbing Code (IPC) and Uniform Plumbing Code (UPC). However, some jurisdictions have specific requirements:

• Some areas require copper within a certain distance of the water heater
• A few municipalities still don't allow PEX (becoming extremely rare)
• Underground installations may require specific PEX types or copper Type L/K
• Always check your local building code before starting a plumbing project

When to Use PEX

• Whole-house replumbing (major cost savings)
• DIY installations (much easier to work with)
• Areas with hard water or aggressive water chemistry (corrosion resistant)
• Cold climates (freeze resistance)
• Retrofitting through existing walls (flexible routing)

When to Use Copper

• Outdoor or sun-exposed runs (PEX degrades in UV)
• Near the water heater (some codes require it)
• When connecting to existing copper (easier to match)
• Commercial or institutional buildings (many specs require copper)
• When maximum longevity and proven track record matter most

Transitioning from Copper to PEX

If you're partially replumbing or adding PEX to an existing copper system, you'll need transition fittings. Options include:

• Copper-to-PEX crimp adapter: One end solders onto copper; the other accepts PEX with a crimp ring.
• Push-fit transition fitting (SharkBite): Pushes onto both copper and PEX without tools. Convenient but expensive.
• Threaded transition: A threaded copper adapter connects to a threaded PEX adapter. Requires Teflon tape or pipe dope on the threads.

When transitioning, use dielectric unions or brass fittings at copper-to-PEX joints to prevent galvanic corrosion between dissimilar metals.

Frequently Asked Questions

Does PEX affect water taste? New PEX can impart a slight plastic taste or odor to water for the first few weeks. Flushing the system thoroughly after installation eliminates this. PEX-A tends to have less taste impact than PEX-B.

Can rodents chew through PEX? Yes, rodents can chew through PEX tubing. In areas with rodent problems, protect PEX runs with metal conduit or use copper in vulnerable locations (crawl spaces, attics).

Is PEX safe for drinking water? Yes. PEX is NSF/ANSI 61 certified for potable water. It does not leach harmful levels of any substance. Extensive testing by independent labs has confirmed its safety.

Can I use PEX for radiant floor heating? Absolutely — PEX is the preferred material for radiant floor heating systems due to its flexibility, durability, and heat resistance (rated for 200°F).