What Does IPS Stand for in Plumbing?
September 9, 2025
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When shopping for pipes, fittings, or plumbing supplies, you might come across the abbreviation IPS. If you’re not a plumber, this can be confusing, especially since plumbing already has so many different terms and standards. So, what does IPS actually mean? Let’s break it down.
IPS: Iron Pipe Size
In plumbing, IPS stands for Iron Pipe Size. It’s a standard method used to measure the diameter of pipes. Originally, this system was developed for iron pipes—hence the name—but it’s still used today across many different materials, including PVC, CPVC, and steel.
The IPS system helps ensure that pipes and fittings made by different manufacturers are compatible with one another, which is important for consistent sizing in plumbing installations.
How IPS Sizing Works
When you see a pipe labeled with an IPS measurement, it refers to the nominal size of the pipe, not the actual outside or inside diameter. For example:
- A pipe marked as 2” IPS doesn’t have an exact 2-inch inside or outside diameter.
- Instead, the measurement is based on standardized dimensions that allow fittings and pipes to connect properly.
This is why sometimes the real measurement of the pipe can seem confusing compared to its “named” size.
IPS vs. Other Pipe Standards
Plumbing has multiple sizing systems, and it’s easy to mix them up. Here’s how IPS compares:
- NPT (National Pipe Thread): This refers to the threaded connections on pipes, not the size of the pipe itself. Many IPS pipes use NPT threads.
- CTS (Copper Tube Size): Used for copper piping and some types of plastic pipes, with a different sizing system than IPS.
- Nominal Pipe Size (NPS): A newer standard that is largely interchangeable with IPS in most modern applications.
Why IPS Matters in Plumbing
Understanding IPS is important because it helps homeowners and contractors:
- Choose the correct fittings for repairs or installations
- Avoid mismatched parts that won’t fit together
- Ensure consistent water pressure and flow in a plumbing system
Final Thoughts
In plumbing, IPS stands for Iron Pipe Size, a standard way of measuring pipe diameter that has been around for more than a century. Even though it originated with iron pipes, the IPS standard is still widely used for PVC, CPVC, and steel piping today. Knowing what IPS means can save you time, money, and frustration when working on plumbing projects.