The pipes that carry water to the taps are usually visible in three or four places in any house, and you can tell most materials apart in under a minute with a coin and a fridge magnet. That matters before you buy, because two of the materials you might find, galvanized steel and polybutylene, are the ones that tend to mean a repipe, and the report engine behind this site prices a whole-home repipe at $4,000 – $15,000.
This is about the supply pipes, the ones under pressure that feed sinks, showers and the water heater. Drains are a separate system; for those, see the guides to cast iron and Orangeburg pipe.
Where to look
Supply pipe shows itself where it connects to something:
- Above the water heater, where the cold line goes in and the hot line comes out.
- Under the kitchen and bathroom sinks, behind the shut-off valves.
- At the main shut-off, usually where the water line comes into the house from the street, in a basement, crawlspace, garage or utility room.
- In an unfinished basement or crawlspace, where runs are often exposed along the joists.
Look in more than one place. Repairs often join new pipe to old, so a short piece of plastic under one sink does not tell you what runs through the walls.
Plastic or metal? Start there
Plastic supply pipe is flexible or lightly rigid and does not ring when tapped. Metal is hard and cold to the touch. From there:
| What you see | What it probably is |
|---|---|
| Flexible plastic in red, blue or white, printed with "PEX" | PEX |
| Rigid plastic, beige or tan, glued joints | CPVC |
| Flexible plastic, usually gray, sometimes blue or black | Possibly polybutylene |
| Metal that scratches orange or pale orange | Copper |
| Gray metal, hard to scratch, a magnet sticks | Galvanized steel |
| Gray metal, soft to scratch, a magnet does not stick | Possibly lead |
The metal tests come from the EPA's own quick check, described in more detail in the lead service line guide. Scratch gently, and only with the seller's permission.
PEX
PEX is cross-linked polyethylene, a flexible plastic tube. It is sold in red, white and blue, and the color is only there to tell lines apart: one maker, Apollo, describes its colors as being "for easy identification of hot, cold and main water lines". Red is not a better pipe than blue.
The surest sign is the printing along its side. A typical listing requires PEX tubing to be marked with the maker's name, "ASTM F876 and ASTM F877 PEX", the pressure rating, the size and the date of manufacture. If you can read "PEX" on the pipe, you have your answer.
CPVC
CPVC is a rigid plastic made to ASTM D2846, the standard for plastic hot- and cold-water distribution systems. Its joints are glued with solvent cement rather than crimped or threaded. FlowGuard, one CPVC maker, explains that CPVC pipe and fittings are made in beige or tan so they are not confused with PVC, which is typically white.
Copper
Copper is easy once you scratch it: the metal underneath is orange or pale orange. Rigid copper water tube is made to ASTM B88 in three wall weights, Type K (heavy wall), Type L (medium) and Type M (light), and the hard tube carries a printed color code to match: green for K, blue for L and red for M. Cerro, a copper tube maker, notes that soft coiled tube does not carry the color marking, so no stripe does not mean it is not copper.
Copper is the reassuring result. Point out anything that looks corroded at a joint, and let your inspector say whether it matters.
Galvanized steel
Galvanized pipe is steel coated with zinc, gray, hard and magnetic, usually joined with threaded fittings. The report engine flags it on houses built through 1969, because it corrodes from the inside out, which shows up as reduced water pressure and discolored water long before it leaks.
Two quick checks on a viewing: turn on a tub tap and a sink tap at once and watch the pressure, and run a tap for a few seconds to see whether the water starts out discolored. Neither proves anything alone, but together with gray, magnetic pipe they tell you what to ask the seller about.
Also check the water utility's record for the line from the street. Under the federal lead rules (40 CFR 141.2), a utility's inventory can list a line as "galvanized requiring replacement", and the lead service line guide explains how to look the address up.
Polybutylene
Polybutylene is a flexible plastic supply pipe, usually gray, sometimes blue or black, and the report engine flags it on houses built from 1978 through 1996. It can raise questions with an insurer, so if you think you have found it, read how to spot polybutylene and what it means for insuring the house before your inspection period ends.
Lead inside the house
Lead supply pipe is gray, soft enough to scratch easily, and does not attract a magnet. Federal law has barred lead pipe in new plumbing and repairs since June 19, 1986 (42 U.S.C. 300g-6), so it is a question for older homes. It is also a question for the service line from the street, which the utility's inventory covers.
Get it in writing from your inspector
A general home inspection covers this. Under the American Society of Home Inspectors Standard of Practice, section 7.1, the inspector must describe in writing the predominant type and material of the interior water service and distribution systems. Ask for it to be named in the report, including where the inspector saw it, and ask the seller for any repipe invoices. If the answer is galvanized or polybutylene, that is the line item to price into your offer.