Plumbing Pipe Materials Explained: PEX, Copper, PVC, and More

Most houses run on more than one pipe material, and the easiest way to make sense of yours is to stop asking “which pipe is best” and start asking “which pipe goes where.” The plumbing in a typical American home splits into three jobs: pressurized supply lines that carry clean water to your fixtures, drain-waste-vent (DWV) lines that carry used water and sewer gases away, and whatever older material a previous era left in the walls. Each job favors different materials, and once you know the sorting logic you can usually name what is in your own home from across the room.

This guide is a map, not a verdict. It names every common material once, tells you where it lives and why it rose or fell out of favor, and then points you to the deeper posts that fight the head-to-head battles. Use it to place your own pipes first, then go read the specific comparison or diagnosis that matters for your house.

Supply-Side Materials: PEX, Copper, and CPVC at a Glance

Supply lines are the pressurized pipes that bring potable water to every faucet, toilet, and appliance, and three materials dominate them in modern homes: PEX, copper, and CPVC.

PEX stands for cross-linked polyethylene, a flexible plastic tubing that has become the most common new-construction supply material because it installs fast, snakes through framing with few fittings, and tolerates freezing better than rigid pipe. It usually comes color-coded: red for hot, blue for cold, and white for either. Color is just a labeling convenience and does not change the pipe’s rating.

Copper is the long-proven metal supply pipe, a reddish-brown rigid line joined by soldered or pressed fittings. It has decades of track record, holds up to heat, and carries no concerns about plastic taste, which is part of why some buyers still prefer it. Its weak point is corrosion in aggressive or acidic water, which can eventually produce tiny weeping holes.

CPVC is a cream or tan rigid plastic rated to carry hot water, which ordinary PVC cannot do. According to manufacturer guidance, CPVC is rated for continuous service up to about 200 degrees Fahrenheit, well above PVC’s roughly 140-degree limit, which is exactly why CPVC is allowed for hot supply and PVC is not.

For the detailed PEX-versus-copper trade-off that most homeowners actually wrestle with, see our guide on choosing between PEX and copper (101). For where CPVC fits against the drain plastics, see our guide on the PVC, CPVC, and ABS distinction (102).

Drain-Waste-Vent Materials: PVC, ABS, and Cast Iron

Drain-waste-vent pipe carries used water, waste, and sewer gas out of the house under gravity rather than pressure, and three materials cover almost all of it: PVC, ABS, and cast iron.

PVC is the rigid white plastic you see most often under sinks and in newer drain stacks. It is solvent-welded with primer and cement, it is inexpensive, and it handles drain and vent duty well. PVC must never carry hot pressurized supply water, since sustained heat approaches its temperature limit.

ABS is the rigid black plastic used for the same DWV job in many regions. It is joined with a single-step black cement and skips the separate primer that PVC needs. Whether your area runs white PVC or black ABS for drains is often a regional code preference rather than a quality difference.

Cast iron is the heavy metal DWV pipe common in older and multi-story homes, prized mainly because it deadens the sound of water rushing through walls. It is durable but can rust and scale internally over many decades. Repairs to cast iron are not a beginner job.

Which plastics your jurisdiction actually permits for DWV varies. Model codes such as the International Plumbing Code list both Schedule 40 PVC and Schedule 40 ABS among approved materials, but some local codes permit only one for drains, so verify your local code before assuming. For the deeper PVC-versus-ABS comparison and why you cannot mix their cements, see our guide on the plastic-pipe distinction (102).

Legacy Materials Still Found in Older Homes (Galvanized, Polybutylene, Lead)

Older houses often hide a fourth category: materials that were standard in their day and are now problems to identify and evaluate.

Galvanized steel was the standard supply pipe for much of the early-to-mid twentieth century. It is a gray, magnetic, threaded metal pipe that corrodes and scales from the inside out, slowly strangling water flow and producing rusty water before it ever leaks. Galvanized is a strong candidate for eventual replacement rather than an emergency. Whether to act on it is its own decision, covered in our guide on galvanized steel pipe (103).

Polybutylene is a gray (sometimes blue, black, or white) flexible plastic supply pipe installed widely from the late 1970s into the mid-1990s, then discontinued. According to the home-inspection reference InterNACHI, polybutylene was manufactured between 1978 and the mid-1990s, and disinfectants such as chlorine in municipal water can react with the material and cause it to become brittle and fail. It is no longer an approved plumbing material. If you suspect polybutylene, the practical move is to have it evaluated by a licensed plumber.

Lead is the most health-sensitive legacy material. Lead service lines and lead solder were used in older systems, and federal law has steadily tightened what counts as lead-free. The EPA notes that the use of pipe, solder, and flux that is not lead-free was prohibited after June 1986, and the lead-free standard was later lowered to a weighted average of 0.25 percent across the wetted surfaces of pipes and fittings. Importantly, the EPA also documents that galvanized pipe located downstream of a former lead service line can keep releasing accumulated lead long after the lead pipe itself is gone, because lead particles lodge in the rough interior scale. If lead is a possibility in your home, this is testing-and-professional territory, not a DIY removal.

How to Identify What Pipe You Have by Color, Markings, and Feel

You can usually identify a pipe without any tools by checking three things: color, whether a magnet sticks, and any stamped markings along the pipe.

• Reddish-brown, rigid, non-magnetic metal with soldered joints is copper.
• Gray, threaded, magnetic metal is galvanized steel. A refrigerator magnet snapping to it is the quick tell, since copper and plastic are not magnetic.
• Flexible plastic tubing in red, blue, or white is almost always PEX. Gray flexible plastic, especially in a home built between roughly 1978 and the mid-1990s, may be polybutylene and is worth a closer look.
• Rigid white plastic on a drain line is PVC. Rigid black plastic on a drain line is ABS. Cream or tan rigid plastic on a hot supply line is CPVC.
• Heavy gray metal drain pipe, often painted, that rings dull when tapped is likely cast iron.

Most rigid pipe also carries printed markings along its length stating the material, standard, and size. Manufacturers such as Uponor and SharkBite print identifiers along PEX, and brands such as Charlotte Pipe stamp PVC and ABS, so reading the stamp confirms what the color and magnet test suggest. When you cannot tell, treat the unknown pipe as a question for a plumber rather than a guess.

Which Material Goes Where in a Typical House

Here is the quick mental model. Supply lines carrying pressurized potable water are usually PEX, copper, or CPVC. Drain-waste-vent lines carrying gravity flow are usually PVC, ABS, or cast iron. Anything else, especially galvanized steel, polybutylene, or lead, is legacy material whose presence tells you something about the home’s age and what may need evaluating.

A single house commonly mixes several of these. It is normal to find copper near the water heater, PEX feeding newer bathrooms, PVC under the kitchen sink, and cast iron in the main drain stack, all in the same building. Renovations add layers over time, so do not expect one material throughout.

The materials also wear at very different rates, and a pipe’s expected service life depends heavily on water chemistry and installation quality, not just the material name. For how long each material is expected to last, see our guide on pipe lifespans (107). If your map is pointing toward replacement rather than repair, the whole-house decision is covered in our guide on when to repipe (106), and the material chemistry behind corrosion is covered in our guide on pipe corrosion (104).

Frequently Asked Questions

How do I know what kind of pipe I have?
Check color, magnetism, and markings. Reddish-brown non-magnetic metal is copper. Gray threaded magnetic metal is galvanized steel. Red, blue, or white flexible plastic tubing is PEX, while gray flexible plastic in a home from roughly 1978 to the mid-1990s may be polybutylene. White rigid drain plastic is PVC, black rigid drain plastic is ABS, and cream or tan hot-supply plastic is CPVC. Heavy gray drain metal that sounds dull when tapped is usually cast iron. Printed markings along the pipe confirm the material, and a plumber can identify anything you cannot.

What is the most common pipe used in homes today?
For new residential supply lines, PEX is now the most widely used material because it is flexible, fast to install, and tolerates freezing better than rigid pipe. Copper remains common where homeowners prefer a proven metal, and CPVC is used for hot supply in some regions. For drain-waste-vent lines, PVC and ABS plastics are the most common in modern construction, with the choice between them often set by local code.

This article is general information, not professional advice. For identification, testing, or any replacement of suspect lead, galvanized, or polybutylene pipe, consult a licensed plumber and follow your local plumbing code.

Sources

EPA, Use of Lead Free Pipes, Fittings, Fixtures, Solder, and Flux for Drinking Water: https://www.epa.gov/sdwa/use-lead-free-pipes-fittings-fixtures-solder-and-flux-drinking-water
EPA, Planning and Conducting Lead Service Line Replacement (lead accumulation in downstream galvanized pipe): https://www.epa.gov/ground-water-and-drinking-water/planning-and-conducting-lead-service-line-replacement
EPA, Basic Information about Lead in Drinking Water: https://www.epa.gov/ground-water-and-drinking-water/basic-information-about-lead-drinking-water
InterNACHI, Polybutylene for Inspectors: https://www.nachi.org/pb.htm
Oatey, What is the Difference Between PVC and CPVC?: https://www.oatey.com/faqs-blog-videos-case-studies/blog/what-difference-between-pvc-and-cpvc
Corzan, What Is CPVC’s Temperature Rating?: https://www.corzan.com/en-us/blog/what-is-cpvcs-temperature-rating
UpCodes, PVC and ABS DWV Pipe and Fittings (IPC approved materials, varies by jurisdiction): https://up.codes/s/pvc-and-abs-dwv-pipe-and-fittings
Charlotte Pipe, Plastics Technical and Installation Manual: https://www.charlottepipe.com/uploads/documents/technical/TM-PL.pdf