How to Tell What Kind of Water Pipes Your Bay Area Home Has

A homeowner in San Jose calls because the bath fills brown in the morning. On the phone, the first thing we ask is not about the water. It is: “What do the pipes look like at your water heater?” They go to the garage with a phone flashlight and describe dull gray pipe with threads at every joint. That answer tells us more than the rusty bath does.

Here is the plain answer. You can usually tell what your water pipes are made of in a few minutes, without opening a wall. Look at the exposed pipe at the water heater, the main shutoff, and under the sinks. Check the color, the type of joints, and whether a magnet sticks.

• Dull gray metal, threaded joints, magnet sticks: galvanized steel.
• Reddish-brown metal, soldered joints, magnet does not stick: copper.
• Gray plastic, flexible, crimped fittings: likely polybutylene.
• Rigid cream or off-white plastic, glued joints: CPVC.
• Flexible plastic, often red or blue: PEX.

The rest of this guide shows where to look, how to tell them apart, and what each one means for your house.

What you need

• A flashlight. A phone light is fine.
• A refrigerator magnet. The stronger the better.
• A coin or key for a gentle scratch test on dull metal pipe.

Look at the pipes that carry pressurized water to fixtures. Ignore the large drain pipes. Those are a separate system.

Where to look

• At the water heater. The cold line in and the hot line out are usually exposed for a short stretch. This is the best single spot.
• At the main shutoff. Often near the front of the house, in the garage, or where the line enters from the street.
• Under kitchen and bathroom sinks. Look behind the shutoff valves, where the pipe comes out of the wall.
• In the crawlspace, garage or basement. Raised-foundation homes often have long runs of exposed pipe under the floor.
• At hose bibs outside. The pipe just behind the faucet can tell you what feeds it.

Check more than one spot. Many houses have a mix, especially if a bathroom was remodeled or part of the house was repiped.

How to tell each pipe apart

Galvanized steel

Looks like: dull gray metal, sometimes with rust spots. Joints are threaded, with fittings screwed on.

Magnet: sticks.

What it means: galvanized rusts from the inside. Over the years the opening narrows and flow drops. Brown water after the tap sits is a common sign. Leaks often start at the threaded joints. Our post on galvanized pipe replacement covers what to do next.

Copper

Looks like: reddish-brown or penny-colored where clean, darker brown with age. Green or blue crust may form at joints. Joints are soldered, so you see a smooth band of silver-gray metal where pieces meet.

Magnet: does not stick.

Which kind: rigid copper pipe comes in different wall thicknesses. The Connecticut Department of Public Health’s fact sheet on copper pipe explains that the type is stamped on the pipe: Type K in green, Type L in blue, and Type M in red, from thickest wall to thinnest. If you can find the printing, it tells you which you have.

What it means: copper can last a long time. Repeated pinhole leaks are the main warning sign. See pinhole leaks in copper pipes for what causes them and when repair stops making sense.

Lead

Looks like: dull gray, soft metal. It is uncommon inside Bay Area homes, but it is worth ruling out on any older service line.

Magnet: does not stick.

How to check: EPA’s Protect Your Tap guide walks you through identifying a lead service line step by step. All you need is a coin or key and a magnet. If you think you have lead pipe, contact your water supplier and follow EPA’s guidance before you drink the water.

Polybutylene

Looks like: flexible plastic, usually gray, sometimes blue or black. Fittings are often crimped with metal or plastic rings.

What it means: polybutylene is no longer used for new supply lines. It has a history of failing at the fittings. Home inspectors flag it, and some insurers ask about it. If you find it, have it looked at.

CPVC

Looks like: rigid plastic, cream or off-white, with glued fittings. Usually printed with “CPVC” along the side.

What it means: it is a modern material. Rigid plastic can crack if it is bumped or bent hard, so handle it gently.

PEX

Looks like: flexible plastic tubing, often red for hot and blue for cold, sometimes white. It bends around corners with few fittings.

What it means: PEX is common in newer construction and in repipes. If your house was repiped with PEX, you likely have years of service ahead.

What each result means for you

• Galvanized: plan for a repipe. The question is when, not whether. Low pressure, brown water or leaks mean sooner.
• Polybutylene: plan for a repipe. Talk to your insurer if you are unsure how they view it.
• Copper, no leak history: probably nothing to do. Keep an eye out for pinholes and green crust.
• Copper with repeated leaks: have the pipe evaluated. A pattern of leaks usually means a repipe.
• PEX or CPVC in good shape: usually nothing to do.
• A mix: find out where the older pipe is. A galvanized trunk line can undo a remodel’s new copper.

Why it matters beyond leaks

Pipe material shows up in places you might not expect.

• Selling the house. Inspectors note galvanized and polybutylene. Knowing first lets you plan. See whether repiping increases your home’s value.
• Insurance. Some insurers ask what your pipes are made of.
• Remodels. If you are opening a kitchen or bathroom wall anyway, that is the cheapest moment to replace old pipe behind it.
• Water heater replacement. The pipe at the heater is often the most corroded. Look at it when the heater is replaced.

If a repipe is in your future

We install two materials:

• Uponor PEX-A with a 25-year parts and labor warranty. Flexible, fewer fittings, fewer wall openings.
• L-grade American copper with a 30-year warranty. Costs more than PEX on the same scope.

Our PEX vs copper guide covers how to choose.

A whole-house repipe is permitted work, followed by a city or county inspection of the new lines. We pull the permit on every whole-house water-supply repipe. Our license is CSLB #1057926.

Mistakes when checking your own pipes

• Looking at only one spot. The pipe at the heater may be new while the rest is not.
• Confusing drain pipe with supply pipe. Large black or white plastic pipe is usually drain. You want the smaller pressurized lines.
• Scratching hard on old pipe. A light scratch is enough. Do not dig into a pipe that is already corroded.
• Assuming a remodel replaced everything. Remodels often stop at the wall.

Questions homeowners ask

Can I tell from the age of the house?

Age gives a hint, not an answer. Many older homes were partly or fully repiped over the years, and some newer ones had problem materials. Look at the pipe itself.

Is the line from the street to the house mine?

In most cases the water supplier owns the meter and the line on its side, and the owner is responsible for the line from the meter to the house. Ask your supplier where its responsibility ends.

Will a home inspection tell me what pipes I have?

An inspector notes the pipe they can see. They do not open walls. A plumber can look at more spots and tell you how the visible pipe connects to the rest.

Next step

If you found galvanized, polybutylene, or copper with a history of leaks, have us take a look. We will tell you plainly what you have and whether a whole-house repipe makes sense. Book online or call (408) 295-4309.