What’s Really Running Through Your Walls?

By Mobile Up! – Your Trusted Partner for Home Maintenance Across Western Washington

THE PROBLEM: YOU DON’T KNOW WHAT YOU DON’T KNOW

Here’s a question for you. When was the last time you thought about the pipes inside your walls?

If you’re like most homeowners in Bellevue, Renton, or Kirkland, the answer is probably “never.” And honestly, that’s normal. Pipes are out of sight, out of mind. They sit behind drywall, under floors, above ceilings—doing their job quietly, reliably, for years.

But then something breaks.

A leak appears. A pipe bursts. A faucet needs replacing. And suddenly, you’re standing at the hardware store staring at fittings, adapters, and connectors, realizing you have no idea what kind of pipe is running through your home.

Here’s the truth: You can’t fix what you don’t understand.

Before you buy a single part or turn a single wrench, you need to know what’s inside your walls. Copper? PEX? PVC? Or worst of all—galvanized steel?

Your pipes are the arteries of your house. Before you perform surgery, you need to know if you’re working with veins or arteries. This guide will teach you how to identify the four most common pipe materials in Western Washington homes. And in the articles that follow, we’ll show you exactly how to work with each one.

THE STORY: WHAT WE FOUND IN A FEDERAL WAY BATHROOM

A few years back, we got a call from a homeowner in Federal Way. Her bathroom faucet was leaking—just a slow drip—and she wanted us to replace it. Simple job, right?

When our team arrived, we shut off the water under the sink and started to disconnect the old supply lines. That’s when we noticed something strange. The pipes coming out of the wall weren’t copper. They weren’t PEX. They were galvanized steel—original to the house, built in 1962.

Inside those pipes? Rust. Thick, flaky, orange-brown rust that had reduced the inner diameter from ½ inch to barely ¼ inch. The homeowner had been complaining about low water pressure for years and never connected it to her pipes.

We explained that replacing a faucet was the easy part. The real issue was the pipes themselves—they were failing from the inside out. The rust wasn’t just restricting flow; it was contaminating her water.

That day, she learned something about her home that she’d never known. And she learned it before a pipe burst and flooded her bathroom—which, given the condition of those pipes, was only a matter of time.

That’s what this series is about. Helping you understand your home before something goes wrong.

THE MOBILE UP GUIDE: 4 TYPES OF PIPES IN PACIFIC NORTHWEST HOMES

Over years of remodeling homes across Western Washington—from mid-century ramblers in Tacoma to new construction in Redmond—we’ve seen every type of pipe. Here’s how to identify what you have.

1. COPPER PIPE – THE GOLD STANDARD

How To Identify It

Copper pipe looks like… well, copper. It has a warm, reddish-brown metallic color. Over time, exposed copper may develop a greenish patina (verdigris) like the Statue of Liberty, but that’s just surface oxidation—not a sign of failure.

Where You’ll Find It

Copper was standard in homes built from the 1950s through the 1990s. In Western Washington, you’ll find it in older neighborhoods like North Tacoma, Capitol Hill in Seattle, and historic areas of Olympia.

Markings To Look For

Look for colored stripes or printing on the pipe:

• Type M (red stripe): Thinest wall, fine for residential water lines
• Type L (blue stripe): Thicker wall, more durable
• Type K (green stripe): Thickest wall, used for underground service lines

How It Connects

Copper connects in two ways:

• Sweating (soldering): A torch melts solder into the joint. This is the traditional method and creates a permanent, leak-proof seal.
• Compression fittings: No torch needed—a threaded nut compresses a ring around the pipe. Good for DIY repairs.

Pros and Cons

• Pros: Durable, long-lasting (50-70 years), doesn’t affect water taste, recyclable
• Cons: Expensive, requires torches for traditional connections, can freeze and burst, may develop pinhole leaks in areas with aggressive water (parts of King County)

The PNW Factor

Copper and our wet climate get along fine—as long as it’s properly installed. The real issue is water chemistry. Some Western Washington water systems (particularly well water in areas like Lakewood and Lacey) can be slightly acidic, which slowly eats copper from the inside.

2. PEX PIPE – THE DIY DREAM

How To Identify It

PEX is flexible, colored plastic tubing. It’s usually red (for hot water), blue (for cold water), or white/clear (for either). Unlike rigid copper or PVC, PEX bends around corners, which means fewer fittings and fewer potential leak points.

Where You’ll Find It

PEX became popular in the 1990s and is now the standard for new construction and remodels. If your home in Redmond, Duvall, or Kent was built after 2000, you almost certainly have PEX.

Markings To Look For

Look for printing on the tubing that says “PEX” followed by a number:

• PEX-A: Most flexible, can be repaired with expansion fittings (pro-grade)
• PEX-B: Slightly stiffer, most common for DIY, uses crimp or clamp rings
• PEX-C: Stiffest, least common

How It Connects

PEX is where DIY plumbing gets easy. No torch. No glue. Just specialized rings and a crimping tool:

• Crimp rings: A copper ring slides over the pipe, you insert a fitting, and a crimping tool squishes the ring tight.
• Clamp rings (cinch rings): A stainless steel band goes around the pipe. A special tool cinches it down.
• Push-fit (SharkBite): Push the fitting onto the pipe—no tools at all. But they’re expensive.

Pros and Cons

• Pros: Flexible (fewer fittings), freeze-resistant (expands slightly instead of bursting), easy to work with, affordable
• Cons: Can be damaged by UV light (don’t store it outside), some rodents chew it, not everyone likes the look of colored tubing

The PNW Factor

PEX is perfect for our climate. It handles the temperature swings from freezing winter nights to summer heat without becoming brittle. And in earthquake-prone Western Washington, its flexibility means it’s less likely to crack during seismic activity.

3. PVC AND ABS – FOR DRAINS, NOT DRINKING WATER

How To Identify Them

• PVC (white or light gray): Rigid plastic pipe used for drains, vents, and cold water lines (but not recommended for hot water inside homes).
• ABS (black): Rigid plastic pipe used almost exclusively for drains and vents. It’s darker and slightly more flexible than PVC.

Where You’ll Find It

Look for PVC or ABS under sinks and in basements. These are your drain pipes—the ones carrying wastewater away, not bringing fresh water in.

How To Identify Schedule 40 vs. Cellular Core

• Schedule 40 (solid wall): Heavier, stronger, used for pressure applications and underground. The pipe walls are solid plastic all the way through.
• Cellular core (foam core): Lighter, less expensive, used for drains inside homes. If you look at the cut end, you’ll see a foam-like center layer.

How It Connects

PVC and ABS connect with solvent cement (glue). The process is simple:

1. Cut the pipe square.
2. Clean the end with primer (purple stuff for PVC, clear for some ABS).
3. Apply cement to both pipe and fitting.
4. Push together and hold for 10-15 seconds.

Pros and Cons

• Pros: Inexpensive, lightweight, easy to work with, doesn’t corrode
• Cons: Can become brittle with age, not for hot water (PVC), UV damage if exposed to sunlight

The PNW Factor

In older homes around Olympia and Tumwater, we still see original cast iron drain pipes. PVC and ABS are the modern replacements—lighter, cheaper, and easier to install. If you’re remodeling a bathroom, switching to PVC or ABS for drains is a smart move.

4. GALVANIZED STEEL – THE OLD NIGHTMARE

How To Identify It

Galvanized steel pipes are gray, metallic, and heavy. They look like what they are—steel pipes coated with zinc to prevent rust. A magnet will stick strongly to them (try this test if you’re unsure).

Where You’ll Find It

If your home was built before 1960—think vintage homes in Everett, Auburn, or Longview—you may still have galvanized pipes. They were standard for decades before copper took over.

How To Spot It

• Magnetic: A refrigerator magnet will stick firmly.
• Threaded joints: Look for hexagonal fittings where pipes connect (not smooth like soldered copper).
• Rust spots: Brown stains around fittings or on the pipe surface.
• Low water pressure: A classic sign that galvanized pipes are rusting shut from the inside.

What Goes Wrong

Here’s the problem with galvanized steel: it rusts from the inside out.

The zinc coating eventually fails. Water contacts bare steel. Rust forms inside the pipe, slowly reducing the inner diameter. What started as a ½-inch pipe becomes a ¼-inch pipe, then a ⅛-inch pipe, then a solid column of rust.

By the time you notice low water pressure, the damage is significant. By the time you see rust in your water, the pipe is failing. And when that pipe finally bursts—not if, when—you’re looking at potential flooding and water damage.

Pros and Cons

• Pros: Extremely durable when new… that’s about it
• Cons: Rusts internally, reduces water pressure, contaminates water, difficult to work with (threaded connections), heavy, expensive to replace

The PNW Factor

In Western Washington’s damp climate, exposed galvanized pipes in crawlspaces and basements rust faster than in drier regions. The combination of high humidity and temperature swings accelerates the corrosion.

Our Honest Advice

If you have galvanized pipes, start planning for replacement. You don’t have to do it all at once—many homeowners replace section by section during remodels—but ignoring them won’t make them last longer.

We’ve helped homeowners in Kalama, Kelso, and Vancouver replace entire homes’ worth of galvanized pipe with PEX. Yes, it’s an investment. But it’s also peace of mind.

THE QUICK IDENTIFICATION GUIDE

Not sure what you’re looking at? Here’s a simple flow chart:

Question	Yes	No
Is it metallic and reddish-brown?	COPPER	Keep going
Is it metallic, gray, and magnetic?	GALVANIZED STEEL	Keep going
Is it flexible, colored plastic?	PEX	Keep going
Is it rigid white, gray, or black plastic?	PVC or ABS	Call a pro—you might have something unusual

THE BOTTOM LINE: KNOW YOUR PIPES

Here’s what we’ve learned from hundreds of home inspections across Western Washington:

Knowledge is protection. The more you know about your home’s plumbing, the less likely you are to be surprised by a costly emergency.

Different pipes need different care. Copper needs protection from acidic water. PEX needs protection from UV light. Galvanized needs… replacement.

Small investments now prevent big expenses later. Testing your water chemistry, inspecting accessible pipes annually, and addressing small issues early costs pennies compared to flood damage.

WHAT’S NEXT? YOUR PIPES DEEP DIVE SERIES

You’ve now identified what’s running through your walls. But knowing what you have is only the first step.

In the upcoming articles, we’ll show you exactly how to work with each type of pipe:

ARTICLE 1 (You Are Here): Pipes 101 – Identify what’s in your walls

ARTICLE 2: Working with Copper – When to Solder, When to Use Compression Fittings

ARTICLE 3: PEX for Beginners – How to Crimp, Clamp, and Connect Like a Pro

ARTICLE 4: PVC and ABS – Proper Gluing Techniques for Drain Lines

ARTICLE 5: Galvanized Steel – How to Spot Trouble and Plan for Replacement

Each guide is packed with real stories from homeowners across Western Washington—from a kitchen remodel in Kirkland to a bathroom renovation in Lacey. You’ll learn what works, what doesn’t, and when to call for help.

YOUR MOVE: START WITH A WALK-THROUGH

Step 1: Grab a flashlight and open your basement door or crawlspace access.

Step 2: Look at the pipes coming in from the street and branching through your home.

Step 3: Use the guide above to identify what you have. Touch them. Magnet test them. Look for colored markings.

Step 4: Write it down. “Copper pipes, built 1985” or “PEX, remodeled 2015” or “Galvanized, original 1950s.”

Step 5: Follow along with our series to learn how to work with your specific pipes.

Here’s the thing about plumbing knowledge: once you understand your pipes, you stop being afraid of them.

A leak is no longer a mystery. A replacement faucet is no longer intimidating. You know what you’re working with, what tools you need, and when the job is within your skills.

That’s what Mobile Up! is all about. We’re not here to make you dependent on us. We’re here to help you understand your home better—so you can make smart decisions about when to DIY and when to call a pro.

If you’re in Bellevue, Everett, Renton, Kirkland, Kent, Federal Way, Auburn, Des Moines, Redmond, Duvall, Olympia, Longview, Kalama, Kelso, Lakewood, Lacey, Tumwater, Vancouver, Tacoma, Fife, or Milton—we’ve been in homes just like yours. We’ve seen the copper, the PEX, the PVC, and the galvanized. We’ve fixed the leaks, replaced the rusted pipes, and helped hundreds of families understand their plumbing.

Your pipes are the arteries of your house. Now you know what they’re made of. You’re already ahead of most homeowners.

If you’re ready to tackle a DIY project, the articles in this series will show you how. And if you run into something beyond your comfort zone? We’re just a call away.

Mobile Up! – Lifting your home, one pipe at a time. 🏠🔧✨

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