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Pipes & Pipe Fittings Guide

Revised: 8/27/19
Grainger Editorial Staff

When it comes to plumbing, choosing the right pipe fittings and tubing for your pipes is very important. Installing the incorrect features can result in an onslaught of issues, ranging from corrosion to downtime or even injury. Learn how to choose the right tubing and pipe fitting types for your plumbing applications with our guide.

Pipe Tubing and Fittings Guide


Pipes are the foundation of all plumbing systems. Without them, materials wouldn’t be able to move in and out of residential and commercial applications. But conduits don’t work alone; they require added fixtures that play vital roles in plumbing operations. Two of those features are tubing and fittings.

Pipe Fittings

Fittings are fixtures used to connect other pipes and tubes. They come in a countless amount of materials, shapes and sizes and are used to attach, join or lengthen pipes. For example, if a system needs to wrap around a corner and doesn’t have the right shape to do so, the right fitting can be placed to safely and securely connect two pipes.

Pipe Tubing

Tubing is similar in the look and style of a pipe itself but pipe tube fittings are typically only used for structural purposes. Unlike pipes, these fixtures aren’t used for the transfer of liquid or gas and their defining sizing specification is the outside diameter.

There is a wide selection of pipe tubing and pipe fitting types, but finding the right ones for your pipes is essential to a working plumbing system. The most important consideration when selecting tubing and fittings is fixture compatibility. Without this, your plumbing applications won’t operate efficiently. Here’s the kind of criteria you need to look out for when choosing pipe tubing and fittings.


Most people use the term “pipe” and “tubing” interchangeably, but they have different purposes. Pipes serve as a vessel for transfer in large plumbing applications. Tubes, on the other hand, are typically used in structural applications that require smaller diameters and are often utilized in features that require precise outside diameters. The right pipe tubing type can provide optimal and cost effective performance for your plumbing applications. Tubing can be made from hard or soft materials. However, tubing usage falls into three different general categories:

  • Fluid transport: tubes that transport fluids from one place to another
  • Structural applications: tubes designed to use in buildings and structures for mechanical properties
  • Electrical sheathing: tubes that are designed around electrical wires or applications to protect against abrasion

Like any other tool, plumbing features are designed to perform specific functions. The first step in finding the appropriate device for your application is by asking yourself the question: What are my needs? Fittings are attached to pipes to provide various functions, ranging from length extension to direction changes and so on. Here are some of the most common pipe fittings and their functions:

  • Connector: connects two pipes
  • Extender: fits inside pipes to extend length
  • Elbow: changes direction of water flow
  • Reducer: changes pipe size to meet hydraulic flow requirements
  • Tee: combines fluid flow from multiple branches
  • Bushing: joins pipes of various sizes
  • Coupling: connects and disconnects of pipes for maintenance or replacement
  • Adapter: extends or changes connection type at the end of a pipe
  • Plug: fits inside to seal pipes
  • Cap: covers the end of a pipe
  • Valve: stops or regulates flow


Since pipes aren’t made from only one material, it’s to be expected that the same goes for pipe fittings and pipe tubing. The use of material for fittings depends on several different factors, including temperature conditions, pressure ratings, cost, etc. However, both fittings and tubing components are typically matched with the material of the pipe itself. The most common materials for fittings are metals and plastics, including brass, copper, steel, black iron, polyvinyl chloride, high-density polyethylene and more.

For tubing, material selection plays a huge role in determining the right kind for your application. Hard, metal pipe tubing is used when pipes need strength and hardness. Copper, aluminum and steel are the most commonly used metals for tubing. These materials are frequently used in plumbing and heating applications for their corrosion resistant durability.

Soft tubing is a more flexible alternative in plumbing systems. The most commonly used plastics are nylon, polyethylene, polypropylene, polyurethane and polyvinyl chloride. Soft tubing offers corrosion resistance, strength and helps reduce pressure leaks.


The proper sizing is essential to a successful fitting and tubing selection. Fitting size is determined by the inside diameter (ID) and outside diameter (OD) of its corresponding connections, measured in inches or millimeters. ID measures the size of the empty portion of the cylinder, and OD sizes the thickness of the tubing wall.

Tubing size is somewhat similar. Also measured in inches or millimeters, the dimensions for tube sizing is determined by the OD, ID and wall thickness, but nominal sizes for tubes are based on the outside diameter.

By carefully and correctly selecting the proper pipe tubing and pipe fitting types for your application so your plumbing systems will be able to operate at peak performance.


JD Squared

Parker Alok


PlumbingSupply Group


The product statements contained herein are intended for informational purposes only. Such product statements do not constitute a product recommendation or representation as to the appropriateness for a specific application or use. W. W. Grainger, Inc. does not guarantee the result of product operation or assume any liability for personal injury or property damage resulting from the use of such products.

The information contained in this article is intended for general information purposes only and is based on information available as of the initial date of publication. No representation is made that the information or references are complete or remain current. This article is not a substitute for review of current applicable government regulations, industry standards, or other standards specific to your business and/or activities and should not be construed as legal advice or opinion. Readers with specific questions should refer to the applicable standards or consult with an attorney.


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