A Guide to Used Steel Pipe Thickness Selection

Picking the right wall thickness for your steel pipe isn’t just a technical detail; it’s a key decision that impacts your project’s safety, strength, cost, and success. Undersize it, and you risk failure. Oversize it, and you’re spending more than you need. In this guide, we’ll break down what thickness selection really means, how it affects performance, and how to confidently choose the right pipe for the job.

Why Choosing Pipe Thickness Matters for Used Steel

One of the biggest differences between two pipes of the same diameter is wall thickness. This measurement plays a major role in steel pipe strength, how much weight it can bear, and how long it will last under real-world conditions.

Thickness selection is all about balancing your application’s demands with budget, availability, and long-term performance. If you’re not sure how thick your pipe should be, you’re not alone. Many buyers skip this step or guess and end up with material that isn’t suited for the job.

Understanding Pipe Wall Thickness: The Basics

Before you choose your pipe, it helps to understand how wall thickness is defined and labeled.

Nominal Pipe Size (NPS) vs. Schedule

Steel pipes are measured by their Nominal Pipe Size (NPS), and wall thickness is categorized by “schedule” numbers (like Schedule 40 or Schedule 80). A Schedule 80 pipe has a thicker wall than a Schedule 40 pipe of the same NPS, meaning it’s stronger and can handle more internal pressure or external load.

Outer Diameter Stays the Same

Here’s where some confusion comes in: For a given NPS, the outer diameter of the pipe stays the same, but as the wall gets thicker, the inner diameter gets smaller. That means a thicker pipe handles more pressure but allows slightly less flow.

Factors Affecting Steel Pipe With Thickness Selection

Choosing the right pipe isn’t just about what fits. You have to think about what your pipe will do and what it will face along the way.

Load-Bearing Capacity: If the pipe is supporting weight, as a piling, beam, or structural column, then wall thickness directly affects its ability to resist buckling or collapse. The more load your pipe needs to handle, the thicker it should be.
Internal Pressure: For applications like water transport, gas lines, or hydraulic systems, internal pressure matters most. Pipes with thicker walls can safely contain higher pressures without leaking or bursting.
Environmental Conditions: Pipes exposed to the elements, especially those underground or underwater, are prone to corrosion. Choosing a slightly thicker pipe gives you more margin if corrosion slowly eats into the wall over time.
Lifespan Expectations: If you’re building a permanent installation or something with a long operational life, investing in a thicker pipe can offer more durability and reduce the risk of replacement down the road.
Budget and Availability: Thicker pipe costs more per foot, especially as steel prices fluctuate. You also need to factor in weight. Heavier pipe costs more to ship and may require different equipment to move and install.

Common Thickness Selection Levels and Where They Work Best

If you’re not sure where to start, here’s a quick breakdown of typical pipe schedules and where they tend to be used.

Schedule 10

Wall Thickness: Thin
Best For: Low-pressure water flow, irrigation systems, fencing, and light-duty frames
Notes: Light and easy to work with, but not suitable for structural or high-pressure use

Schedule 40

Wall Thickness: Standard
Best For: Plumbing, construction framing, agricultural applications, handrails
Notes: Most commonly used schedule for general-purpose projects

Schedule 80

Wall Thickness: Thick
Best For: Pressurized systems, industrial pipelines, structural supports
Notes: Heavier and stronger than Schedule 40; ideal for more demanding environments

Schedule 160 and Beyond

Wall Thickness: Extra thick
Best For: High-pressure oil, gas, or chemical systems
Notes: Often used in very specific, high-performance industrial settings

How to Measure Pipe Thickness

If you’re sourcing used steel pipe, you’ll want to verify wall thickness before buying. Here’s how to check:

Use a Caliper or Micrometer: These tools measure the distance between the pipe’s inner and outer walls to determine the exact thickness. Be sure to measure in multiple spots to account for wear or corrosion.
Compare to Pipe Schedule Charts: Once you have your measurement, reference a schedule chart to match it to the correct NPS and schedule. This ensures you’re getting the specs you need for your application.
Ask for Verification from Your Supplier: A reputable supplier like Steel Pipe Pros will have already tested and documented wall thickness for their used steel pipe. Don’t hesitate to ask for that data.

Looking to learn more about thickness selection and general sizing when it comes to used steel pipes? Check out this helpful guide.

Selecting and Sizing Used Pipe

Mistakes to Avoid When Choosing Pipe Thickness

Thickness selection mistakes can cost you time, money, or worse, structural failure. Here are some of the most common pitfalls to avoid:

Assuming all pipe of the same diameter has the same wall thickness
Guessing instead of measuring or asking
Buying based on price alone without checking structural or pressure needs
Overbuilding when you don’t need to, wasting budget on pipe that’s thicker than necessary
Undersizing for load-bearing or pressure systems

Getting the right pipe thickness is a blend of math, use case, and experience. When in doubt, ask your supplier for guidance based on your intended application.

Thickness Selection for Common Applications

Still not sure what you need? Here’s a quick reference for popular applications and the typical schedules used:

Fencing and posts: Schedule 10 or Schedule 40
Water irrigation lines: Schedule 40
Underground conduit: Schedule 40 or Schedule 80 (if moisture is a concern)
Structural columns or frames: Schedule 80 or thicker
Oil and gas pipelines: Schedule 80 or Schedule 160
Pressure vessels or fluid transport under pressure: Schedule 80 minimum

Why Thickness Matters More in Used Steel Pipe

When dealing with used pipe, thickness selection takes on even more importance. Depending on its history, used pipe may have some wear, minor corrosion, or slight wall thinning. That’s why going too thin isn’t just risky; it could lead to unexpected failure.

A supplier that tests and verifies each pipe’s wall thickness can help you buy with confidence, knowing exactly how much integrity remains in the steel.

Get the Right Size Used Steel By Consulting With Steel Pipe Pros

Thickness selection may sound technical, but it’s one of the most practical parts of buying used steel pipe. Choosing the right wall thickness affects everything from safety to performance to long-term costs. The more you know going in, the better decisions you can make.

Steel Pipe Pros offers a deep inventory of tested used steel pipe in every wall thickness you need. We’ll help you choose the right size for your application and make sure your material is strong, safe, and ready to go. Skip the guesswork. Get pipe that fits your specs and your budget. Reach out today and let’s size it right together.