One of the more misunderstood items that often gets flagged during a home inspection is old galvanized piping. When I inspect a house with galvanized piping, there are no symptoms of low water pressure or rusty water, but it is still reported because there is some likelihood these issues will occur in the future. 

What Is Galvanized Pipe?

Galvanized pipes are steel pipes that have been dipped in a protective zinc coating to prevent corrosion and rust. Galvanized piping was commonly installed in homes built before 1960. When it was invented, galvanized pipe was an alternative to lead pipe for water supply lines.

Galvanized steel can be made into a strong plumbing or tubing material -- one that resists corrosion from exposure to water or the elements. It has been used for water-supply pipes or as strong tubing for outdoor applications.

Galvanized pipe has been coated with a layer of zinc. The zinc provides a barrier against corrosion, so the pipe may be exposed to outdoor environmental elements. The protective barrier proves equally effective against damage from indoor humidity.

Also Read: how long do galvanized pipes last

What Do Galvanized Pipes Look Like?

When first installed, galvanized pipes look like nickel in color. But as they age, galvanized pipes may appear much duller, lighter, or darker, depending on their environment. We’ve also seen homes with painted water pipes, so it can be hard to tell at first glance.

To correct over 70 years’ worth of municipal lead piping, city builders found galvanizing to be the easiest solution. Between the end of World War II and 1960, galvanized water supply piping became the most common material in homes to provide potable (drinking) water.

What’s so great about it? The design of galvanized pipes helps prevent corrosion and rust on these steel metal pipes. By dipping lead pipes into molten zinc, corrosion and rust, by all appearances, seemed to diminish completely.

Also Read: replacing galvanized water pipes

How Long Do Galvanized Pipes Last?

It’s hard to say. In the early years of using this protective piping, people thought it would last upwards of 100 years. However, a poor galvanizing technique can dwindle that time frame down to 30-40 years.

Considering galvanized pipes haven’t been installed in homes since the 1980s (at the very latest), that means your pipes have around 40 years of wear and tear. Even if the galvanizing job is exceptional, there is likely a significant amount of corrosion in your lines.

Also Read: cost to replace cast iron plumbing

Galvanized Steel Pipe Dimensions

Galvanized steel pipe comes in a variety of dimensions and sizes. When you buy it, you’ll want to measure its diameter by nominal size. To find the nominal size, measure the inside diameter of the pipe. Most nominal pipe sizes run between ¼ and 2 ½ inches.

If you do not have access to a cut end to measure inside the pipe, you can estimate the nominal size of a pipe by measuring its outside. Keep in mind, however, that you’ll have to account for wall size, which may be different from pipe to pipe.

The rule of thumb says to measure the outer circumference and divide by pi (3.14). If you have a standard pipe, subtract ¼ inch from the wall. For an extra strong pipe, subtract ⅜ inch.

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Can You Paint Galvanized Steel Pipe?

Painting galvanized steel pipe isn’t easy. The paint does not readily adhere to the zinc coating. One solution is to clean the pipe thoroughly, then rub it down with white vinegar. The vinegar interacts with the metal and makes it more adhesive for paint.

If you start painting galvanized steel pipe, do not use alkyd-based paints or oil-based primers. Instead, go with a primer and acrylic latex paint.

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