What Are Pipes Made of: Complete Guide for Homeowners

Open the wall behind any 1955 ranch house and you might find galvanized steel feeding the kitchen, cast iron handling waste, and a patch of copper installed during a 1989 remodel. Modern homes built since 2010 increasingly run PEX from end to end and PVC for drains. Understanding what are pipes made of matters most when a leak appears, because the patch material has to match the existing system or include a transition fitting. The wrong combination corrodes within months and starts the cycle over.

Copper: The Long-Standing Standard

Copper has carried residential water since the 1930s and still holds 23 percent of new construction installs. Three thickness grades cover home use:

• Type M: thin-wall, used for above-ground residential water lines, $2.85 to $4.20 per foot for 1/2-inch
• Type L: medium-wall, used for underground or commercial work, $3.60 to $5.50 per foot
• Type K: thick-wall, used for service lines from the street main, $4.80 to $7.20 per foot

Joints are sweat-soldered with lead-free solder (95/5 tin-antimony) or pressed with ProPress fittings. Lifespan runs 50 to 70 years in non-acidic water. Acidic well water under pH 6.5 eats through copper in as little as 15 years, which is why testing before installation matters.

PEX: The Flexible Workhorse

Cross-linked polyethylene tubing (PEX) became code-approved nationwide in 2002 and now leads new residential installations. Three types exist:

• PEX-A: made by the Engel method, most flexible, kink-resistant, Uponor and Rehau brands, $0.95 to $1.45 per foot
• PEX-B: made by the silane method, slightly stiffer, NIBCO and Apollo brands, $0.55 to $0.85 per foot
• PEX-C: made by electron beam, least common, $0.60 to $0.90 per foot

Connections use expansion fittings (PEX-A) or crimp/clamp rings (PEX-B and PEX-C). PEX resists chlorine, won’t burst from freeze events, and runs through joists with fewer connections than copper. UV exposure breaks down PEX in 30 to 60 days outdoors, so it must stay inside walls or buried.

PVC and CPVC: Drains and Hot Lines

Polyvinyl chloride (PVC) handles drain, waste, and vent (DWV) lines in nearly every home built since 1980. Schedule 40 white PVC in 1.5 to 4-inch diameters costs $1.20 to $4.80 per foot. Solvent-welded with PVC primer and cement, the joints cure to monolithic strength in 2 to 24 hours depending on diameter and temperature.

Chlorinated PVC (CPVC) handles hot supply lines up to 200 degrees Fahrenheit, though PEX has largely displaced it in new construction. CPVC remains in many 1990s and 2000s homes, identifiable by its cream or beige color versus PVC’s white.

Cast Iron: The Old-House Drain Material

Cast iron drain stacks ruled residential construction from the late 1800s through the 1980s. Hub-and-spigot joints were sealed with oakum and molten lead, while no-hub cast iron used neoprene couplings with stainless steel bands. A 3-inch cast iron stack costs $14 to $20 per foot and lasts 75 to 100 years in non-corrosive soil.

Cast iron dampens water-flow noise dramatically better than PVC, which is why high-end builders still spec it for the soil stack behind primary bathrooms. The trade-off is weight (one 10-foot section weighs around 60 pounds) and the heavier labor cost to install.

Galvanized Steel: Phase-Out Material

Galvanized steel pipe ruled water supply from 1900 to 1960 but has been universally phased out. The zinc coating breaks down internally, creating tubercles that restrict flow and shed iron particles into drinking water. If your home still has galvanized supply, expect water pressure to drop steadily as scale builds.

Replacement is the only fix. Whole-home repipe with PEX or copper runs $4,500 to $14,000 depending on house size, finished walls, and accessibility.

Brand Spotlight: Uponor AquaPEX

Uponor AquaPEX-A and ProPEX expansion fittings have set the bar for residential PEX-A systems. The expansion tool stretches the pipe end over a ring, then the polymer memory shrinks back over the brass fitting in 30 to 90 seconds, creating a connection rated for 100 psi at 180 degrees Fahrenheit. Lifetime warranty on materials covers the system installed to manufacturer specs, and Uponor has paid out claims on installations going back to the early 1990s.

Specialty Materials in Modern Homes

Beyond the big five, you’ll encounter:

• Black iron: natural gas lines, 1/2 to 1-inch sizes, threaded connections
• CSST (corrugated stainless steel tubing): flexible gas line in newer homes
• ABS (acrylonitrile butadiene styrene): black drain pipe accepted in some Western states
• HDPE: outdoor underground water service from the meter to the house

How to Identify Pipes in Your Walls

Visual cues identify most materials quickly:

• Copper: reddish-orange, often greenish patina on exposed runs
• PEX: red, blue, or white flexible plastic with printed markings every 12 inches
• PVC: rigid white plastic, large diameters, solvent-cement joints
• CPVC: cream or beige rigid plastic, smaller diameter
• Galvanized: dull gray threaded steel, magnetic
• Cast iron: black, heavy, threaded or hub joints, magnetic

Lifespan and Replacement Reality

Expected service life by material under typical residential conditions:

• Copper: 50 to 70 years in neutral pH water, 15 to 25 years in acidic well water
• PEX: 40 to 50 years projected (formulated in 1968, oldest installs still in service)
• PVC drain: 50 to 100 years if not exposed to UV
• CPVC supply: 50 to 75 years if not subjected to high chlorine
• Cast iron drain: 75 to 100 years
• Galvanized steel supply: 40 to 50 years (most installs from 1960s now failing)

If your home has any galvanized supply remaining, plan a repipe within the next 5 to 10 years before pinhole leaks force emergency response.

Final Word

Knowing what are pipes made of in your home helps you spec accurate repairs, anticipate replacement needs, and avoid material mismatches that fail. For new construction or whole-home repipe, PEX-A is the modern default for supply and PVC for drains. For older homes, identify the existing system first and match repairs with proper transition fittings to keep galvanic corrosion in check.