Galvanized pipes in older homes: when it's time to repipe

Galvanized steel water pipe rusts from the inside, and over decades the inside slowly narrows. Once you’re seeing pressure that keeps getting worse, brown water, or leaks at the threaded joints, it’s time to start planning a repipe, usually with PEX or copper. Having galvanized pipe isn’t an emergency by itself. But pipe from the 1950s and early 60s is due for replacement.

Why so many houses around Huntsville have it

Huntsville grew fast in the 1950s and 60s with Redstone Arsenal and the space program, so there are a lot of houses from that era. Homes built then, here and nearly everywhere else, commonly went in with galvanized steel supply pipe and cast iron drains.

Some of those houses have been fully repiped. A lot have been repiped in pieces over the years, so you can find copper at the water heater and galvanized in the crawlspace in the same house.

How to tell if your pipes are galvanized

Look at the water lines at the water heater, under the sinks, and in the crawlspace if you have one. Galvanized pipe has a few giveaways:

• It’s a dull gray metal, not the orange-brown of copper and not plastic.
• The fittings are threaded. At every joint you’ll see the pipe screwed into an elbow or coupling.
• A magnet sticks to it. A fridge magnet works fine. Copper and plastic won’t hold one.
• If you scratch it lightly with a key or screwdriver, the scratch stays a dull gray.

Don’t confuse it with gray plastic pipe, which is a different problem. If it’s flexible and plastic, read our post on polybutylene pipes instead.

If the magnet won’t stick. Dull gray metal pipe that a magnet won’t stick to, and that scratches to a shiny silver, could be lead, especially on the line coming in from the meter. Don’t guess on that one. Call your water utility or a plumber and have it checked.

How galvanized pipe fails

Galvanized pipe is steel with a zinc coating. Over the years the zinc wears away and the steel underneath starts to rust. Rust and mineral buildup collect on the inside walls, and the opening gets smaller and smaller. You can’t see any of this from the outside. The pipe can look fine and be half closed up inside.

Here’s what that looks like day to day:

• Water pressure that’s slowly gotten worse over the years
• Brown or rusty water, especially first thing in the morning or after you’ve been out of town
• Leaks at the threaded joints, since the threads are the thinnest part of the pipe wall
• Good pressure at one end of the house and bad pressure at the other

That last one usually means part of the house has been repiped, or one run has clogged up worse than the rest. If weak pressure is your main complaint, our post on low water pressure causes covers the other things worth ruling out first.

Do you have to replace all of it?

Not always. A partial repipe replaces the worst sections, like a leaking run or the lines feeding one bathroom. It costs less up front and can buy you time.

The catch is that the galvanized you leave in place keeps rusting. You can end up paying for a few partial jobs over the years when one whole-house job would have handled it. Where new copper meets old steel, a plumber also has to use a dielectric fitting between them, because the two metals corrode each other when they touch.

Our take: if you’ve got symptoms in more than one part of the house, a whole-house repipe usually makes more sense. If it’s one leaky section and everything else is working fine, a partial can be reasonable.

Most repipes today are done with PEX. It’s flexible, so it can be fished through walls and the crawlspace or attic without opening up every wall. Copper is the other common choice. It has a long track record and usually costs more in materials and labor. What a job costs depends on the size of the house, how many bathrooms you have, and how easy it is to get under or over the house. We’ll give you a price before we start.

Don’t forget the line from the meter to the house. In Huntsville, that pipe belongs to the homeowner, and in an older house it may be galvanized too.

What about the cast iron drains?

That’s a separate question. Cast iron drains in homes of this age are sometimes fine for decades. Other times they’re cracked, badly scaled inside, or rusted thin along the bottom. You can’t tell by looking at the outside of the pipe.

A camera inspection tells you. A plumber runs a camera through the drain and you both watch what’s in there. Don’t replace cast iron just because it’s old. Replace it if the camera shows it’s failing.

You don’t need to call anybody tomorrow about galvanized pipe. It’s a lot easier to pick the date yourself than to let a leak pick it for you.