01At a glance
| Material | Typical use | How to recognize it | Potential issues | Inspection considerations |
|---|---|---|---|---|
| Cast iron | Drain, waste, vent and building sewer, especially in prewar buildings | Heavy, dark, thick-walled; hub joints (older) or no-hub bands (newer) | Internal scale that narrows the bore; rust-through along the bottom of horizontal runs; cracks | Sewer camera inspection; visual check of exposed sections and joints |
| Galvanized steel | Older water supply lines; some older drains | Gray metal with threaded joints; a magnet sticks to it | Internal corrosion that reduces flow; rusty or discolored water; leaks at threads | Condition assessment; flow and pressure checks at fixtures |
| Copper | Water supply; common from mid-20th century renovations onward | Reddish-brown, or green where oxidized; soldered joints | Pinhole leaks and corrosion in some conditions; joint failures | Leak inspection; look for green deposits or staining at joints |
| Lead | Older water service lines (street to building), and some old drain bends | Dull gray, soft; a scratch shows shiny silver; a magnet does not stick | A health concern for drinking water rather than a mechanical one | Service-line material check; DEP map (NYC) or utility inventory (NJ) |
| PVC / ABS (plastic drain) | Drain and vent in newer work and renovations | White (PVC) or black (ABS) plastic; glued joints | Joint and installation issues; mixing materials incorrectly; some uses restricted by local code | Visual inspection; check transitions to older pipe |
| PEX | Water supply in newer work and repiping | Flexible plastic tubing, often red/blue; crimp or expansion fittings | Fitting and installation quality; damage from UV exposure or nearby heat sources | System assessment; check fittings and support |
| Clay (vitrified) | Older building sewers outside the building, mostly in the suburbs | Rarely visible; seen on camera as short segments with many joints | Root intrusion at joints; offset or cracked sections | Sewer camera inspection |
Which materials are permitted for new work depends on the jurisdiction's plumbing code (NYC Plumbing Code; NY State Uniform Code outside NYC; National Standard Plumbing Code in NJ). Ask a licensed plumber.
02Why most older buildings have a mix
Cutaway of old galvanized pipe: decades of corrosion narrow the opening.
A 1900 rowhouse might have its original cast-iron stack, galvanized branches from a mid-century bathroom, copper from a 1990s kitchen and PEX from a recent renovation. Transitions between materials need the right fittings, and leaks often show up there first.
03Symptoms that point to the pipe
| Symptom | May suggest | Related guide |
|---|---|---|
| Weak flow at one or several fixtures; rusty water after the tap sits | Corroded galvanized supply | Low water pressure |
| Recurring slow drains on a lower floor | Scale in cast-iron drain lines | Drain cleaning |
| Rust stains or damp spots below a horizontal drain | Cast iron rusting through | Pipe repair |
| Small spray or drip with green deposits | Pinhole leak in copper | Leak detection |
| Gray, soft pipe where water enters the building | Lead service line | Lead service lines |
04Next steps
If you are buying an older property or planning a renovation, a plumbing assessment and a sewer camera inspection give you evidence before decisions are locked in.
Sources & review
Last reviewed . General information, not legal or engineering advice. Rules change and individual buildings differ.