Quick answer
Copper is dull brown and shows orange when scratched. PEX is flexible plastic, often red, blue or white. CPVC is rigid tan plastic. Galvanized steel is dull gray, magnetic and threaded. Polybutylene is usually gray plastic stamped PB2110. Drains are usually black ABS or white or gray PVC. Check exposed pipe near the water heater or main shutoff.
How to check safely
Start with pipe you can already see: near the water heater, at the main shutoff, under sinks, and in an unfinished basement or crawlspace. The pipe that enters the house usually comes through a wall or floor near the meter or main valve. Look at color, texture, fittings and any printing on the pipe.
For metal, a city guide from Dudley, Massachusetts suggests two simple tests. Scratch a small spot to expose bare metal (sand it if painted), and see whether a magnet sticks. Do not cut into pipe or disturb insulation or wrapping you cannot identify. Keep clear of the water heater flue, which gets hot. Also be careful not to confuse water pipes with gas pipes, which can look like galvanized steel. If you ever smell gas, leave the house and call 911 or your gas utility. When in doubt, a plumber can identify it in minutes.
Copper
Copper is dull brown on the surface, and scratching it shows an orange color like a penny. A magnet does not stick, and tapping gives a metallic ring, according to the Dudley guide. Saint Paul Regional Water Services says copper began to appear in the 1930s and was used most extensively from the 1960s onward.
The main concern sources raise is pinhole leaks, covered in our guide on that topic. Lifespan figures disagree. This Old House, citing the International Association of Certified Home Inspectors, lists copper water lines at 70 years. Mr. Rooter says copper typically lasts 20 to 50 years, with most pinhole leaks showing up around 25 to 30 years. Water chemistry and pressure likely explain part of the gap.
PEX and CPVC
PEX is cross-linked polyethylene, a flexible plastic tube. SupplyHouse explains that potable PEX is commonly red for hot, blue for cold and white for either, and that color does not change its ratings. Some red or white PEX includes an oxygen barrier for heating loops and is generally not for drinking water. Saint Paul says homes built since the late 1990s are mostly plumbed with it. No source we opened gave a reliable PEX lifespan. This Old House lists plastic water lines at 75 years without saying what plastic that covers, so treat it cautiously.
CPVC is a rigid plastic that is described in the PHCP Pros article as tan pipe and is joined with solvent cement. A Lubrizol author, writing in PHCP Pros, says commercial CPVC production began in 1959, it entered national plumbing codes between 1978 and 1982, and a more ductile formulation arrived in 1991. The article is from a company that sells CPVC, so it favors the product. It says most failures trace to installation errors, such as fittings that were pushed together but not properly cemented, and it describes the original CPVC as rigid and harder to work with.
Galvanized steel
Galvanized pipe is steel coated with zinc. It looks dull gray, is hard to scratch, sticks to a magnet and usually has threaded fittings, per the Dudley guide. Saint Paul gives its era as roughly the 1880s to the 1960s, and the East Bay Municipal Utility District in California says it was common before the 1960s.
Both explain the problem. Once the zinc wears away, the pipe corrodes from the inside, which can narrow it, lower pressure, discolor water and eventually cause leaks. Dudley adds that galvanized pipe can trap lead from older upstream lead pipes and release it later. Sources differ on timing. Saint Paul says galvanized pipe is likely reaching the end of its life, while EBMUD says it can last many years before failing. Pressure that has slowly dropped and rusty water are the usual clues.
Polybutylene
Polybutylene (PB) is a plastic supply pipe most often gray, though it also appears white, silver, black or blue. InterNACHI, the home inspector association, says it was made from 1978 to mid-1995 and is usually stamped PB2110. InterNACHI cautions against confusing it with PEX, PVC, CPVC, polyethylene or copper, and SupplyHouse notes that gray plastic pipe is often polybutylene, an older product with a different inside diameter and chemistry than PEX.
The cause of PB failures is itself disputed. InterNACHI reports that University of Illinois at Chicago studies found certain disinfectants can react with the plastic, causing flaking and cracks, while manufacturers argue most leaks occur at joints. Class-action suits against manufacturers succeeded. Because PB can also appear at connections with other pipes, such as bathroom stub-outs, the whole system is worth checking.
Drain pipes: PVC and ABS
Drain, waste and vent pipes are different from supply pipes. Ferguson, a plumbing supplier, says ABS is solid black and PVC is typically white or dark gray, and both replaced older cast iron and lead drain systems. They use different cements, and standard cement will not bond one to the other, so mixing them needs a proper mechanical coupling.
If you are unsure whether a drain line is ABS or PVC, color is the first clue, but a plumber can confirm before any repair that joins the two.
Which pipes lead to repiping decisions
No source we reviewed gives a single rule. Galvanized steel and polybutylene come up most often in repiping discussions because of internal corrosion and the failure history described above. Copper becomes a repipe question mainly when pinhole leaks repeat, which Mr. Rooter says may make a full repipe more cost effective than patching. Lubrizol's author attributes CPVC failures mostly to installation errors rather than the material, which is a manufacturer-side view.
A plumber can look at the age of the house, what the pipe is, how many leaks there have been, and how much of the system you can see. Ask for the reasoning in writing.
When to call Pyper Plumbing
If you cannot tell what your pipes are, notice rust-colored water, falling pressure, or repeated leaks, Pyper Plumbing can help with leak detection and repair, emergency repair and repiping in Snohomish, Skagit, Whatcom and Island counties. Call right away if water is actively leaking and shut off the main valve while you wait.
Common questions
How can I tell PEX from polybutylene?
Check the markings and color. Polybutylene is usually gray and stamped PB2110, per InterNACHI, while potable PEX is commonly red, blue or white, per SupplyHouse. If the color is ambiguous, have a plumber confirm.
Is gray plastic pipe always polybutylene?
No. SupplyHouse notes gray plastic pipe is often polybutylene, and other plastics come in gray too. Look for PB2110 stamping and ask a plumber if unsure.
Does old pipe have to be replaced right away?
Not necessarily. Sources describe age and material as warning signs, but leaks, low pressure and discolored water are what usually prompt action. An inspection of your own pipes is the better guide.
Sources
Facts in this guide come from the following references. Local rules and manufacturer instructions can differ, so follow your utility and your equipment manual.
- Saint Paul Regional Water Services, Plumbing information for homeowners
- Town of Dudley, MA, Steps to identify the pipe material
- East Bay Municipal Utility District, Galvanized iron pipes
- InterNACHI, Polybutylene for inspectors
- SupplyHouse, The colors of PEX tubing
- PHCP Pros, A history of CPVC in residential plumbing
- Ferguson, ABS vs PVC pipe
- This Old House, How long do appliances and parts of your home last
- Mr. Rooter Plumbing, What causes pinhole leaks in copper pipes
This guide is general information, not a substitute for an on-site inspection. If you smell natural gas, leave the building and call 911 or your gas utility. Pyper does not perform gas line work.
