Types of Plumbing Pipes: Copper, PEX, PVC, Cast Iron and More
By Mike Holt, NJ Master Plumber · January 17, 2025 · 3 min read · Updated November 1, 2026
Quick answer
Homes use two groups of pipe. Water supply lines are usually copper, PEX or CPVC, with galvanized steel or polybutylene in some older homes. Drain, waste and vent lines are usually PVC, ABS or cast iron. Material suitability depends on application, listing, manufacturer instructions and NJ code. Service life varies, and galvanized steel and polybutylene are the two most likely to need attention.
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Every house has two separate pipe systems. Supply pipes bring clean water in under pressure. Drain, waste and vent pipes carry used water out by gravity. Each system uses different materials, and older Central New Jersey homes often have a mix from different decades.
What are the types of plumbing pipes?
| Pipe | Looks like | Generally used for | Lifespan (varies) | Notes |
|---|---|---|---|---|
| Copper | Orange-brown metal, green with age | Water supply | Decades | Handles heat; hard water and acidic water can cause pinhole leaks |
| PEX | Flexible plastic, red, blue or white | Water supply | Decades | Fewer fittings, easy to run through walls; keep out of sunlight |
| CPVC | Rigid cream or tan plastic | Water supply, hot and cold | Decades | Can get brittle with age |
| PVC | Rigid white plastic | Drains, vents, outdoor cold water | Decades | Not for hot water supply lines |
| ABS | Rigid black plastic | Drains and vents | Decades | Common in newer homes |
| Cast iron | Heavy black or dark gray metal | Drains and sewer lines | Decades, sometimes many | Quiet, but can rust through and crack with age |
| Galvanized steel | Gray metal with threaded joints | Water supply in older homes | Often shorter than other metals | Rusts from inside; lowers pressure |
| Polybutylene | Flexible gray plastic | Water supply, about 1978 to 1995 | Unpredictable | Known for failing at the fittings |
Material suitability depends on application, listing, manufacturer instructions and NJ code. For more on how long each one may last and what shortens it, see how long do pipes last.
Which pipes are used for water supply?
Copper has been the standard for decades. It's durable and handles heat, but very hard or acidic water can wear it from the inside and cause pinhole leaks. PEX is common in new work because it bends around corners with fewer joints. CPVC shows up in some homes from the 1980s and 1990s.
Galvanized steel and polybutylene are the two to watch for. Have them looked at if your home still has them.
Which pipes are used for drains and sewer lines?
Older homes usually have cast iron drain stacks and sometimes clay sewer pipe outside. Cast iron is heavy and quiet, but after decades it can rust through along the bottom of the pipe or crack at the joints. Newer homes and most repairs use PVC or ABS plastic, which doesn't rust and is lighter to work with. Old drain lines that keep clogging are worth a sewer camera inspection to see what shape they're in.
How can you tell what pipes you have?
- Start where the water main comes into the house, usually through the basement wall near the meter.
- Scratch the surface lightly with a coin. Copper shows a shiny penny color. Galvanized steel shows silver-gray.
- Try a magnet. It sticks to galvanized steel and cast iron, not to copper, brass or plastic.
- Look at the joints. Threaded joints usually mean galvanized steel. Soldered joints mean copper. Crimped rings or clamps mean PEX.
- Check for printing on plastic pipe. PEX, CPVC and PVC usually have the type stamped along the side.
Which pipes should you replace?
Galvanized steel and polybutylene are the first to ask about, ideally before a leak forces the issue. Copper and cast iron with repeated leaks or heavy corrosion are next. If you're remodeling, it's a good time to look at old pipe while the walls are open. Read the signs your house needs repiping for what to look for.
Not sure what you have?
Our team can look at the pipe in your home and tell you honestly what we see. Contact us to confirm whether we handle your scope and materials. See our repiping and pipes and plumbing pages, or call 908-873-6686.
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Stop and call us if
- You find gray galvanized steel or gray plastic polybutylene supply pipe.
- Leaks keep showing up in different places.
- Copper pipe has green crust or pinhole leaks, or cast iron drain pipe is cracked or rusting through.
- You're remodeling and the walls will be open.
Call 908-873-6686.
Michael Holt
Owner and operator of Plumbing Doctor, NJ Master Plumber (Lic. #36BI01345600) and U.S. Marine Corps veteran.
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