air hose fittingsIf you own an air compressor and you need to replace air hose fittings, or even if you’re thinking about installing a permanent system for a shop, then air compressor hose fitting types and sizes will be one of your major concerns.

While most consumer air compressors, tools, and hose systems do come with standard fitting sizes, it is important that you understand what these sizes are, along with the common measurements that you will be exposed to.

Air hose couplings and other connectors that are used for compressors, will all follow a system that is known as the NPT fitting standard.

This standard means that if you are selecting equipment that is measured with standard air fitting types, then it will be compatible with your other fittings, especially the pre-installed couplings that come on your air compressor.

We will first look at the size chart and some of the most common air fitting hose sizes, and then continue on to some of the air compressor fitting types and accessories that you might need when upgrading your system or replacing any worn parts.

Air Hose Fittings: The NPT Size Chart for Air Compressors

The national pipe thread taper, otherwise known as American standard pipe, doesn’t just refer to the size of a connector, but also the size of the thread on any connector.

The thread size is especially important, because non-standard fittings may not provide a full seal, and will allow air to escape from your hose lines and connectors.

As you probably know, this will greatly reduce the efficiency, air flow, and pressure that an air compressor is able to provide to any pneumatic tool that you have connected to your system.

While it is fairly easy to understand the fitting types for industrial and automotive connectors, it is still beneficial to be aware of the NPT fitting chart and how it relates to pipes and connectors of all types.

NPT fitting chart sizes are provided in inches, and include threads per inch and outside pipe diameter. Manufacturers that advertise NPT fittings will be required to conform to these figures with a high level of accuracy.

Below you can have a look at a table that shows the most common NPT thread sizes and their respective threads per inch count and the actual measurement of their outside diameter (OD).

Also, in this article you wil find a more elaborate explanation as well as an expanded version of the table containing more NPT standard thread sizes.

Pipe Size (Inches)Threads Per InchOutside Pipe Diameter
1/827.405
1/418.540
3/818.675
1/214.840
3/4141.050
111-1/21.315

And here’s a useful video we found on youtube to help you understand better how you should correctly measure pipe threads.

How to Determine the Size of an Air Compressor Fitting Port on a Tool or Connector You Already Own

You may already have tools and connectors with working ports, but you may have lost the original documentation or packaging that states the exact air hose fitting sizes.

This can obviously be problematic when it comes to fitting a new hose or replacing a connector.

Most common tools use a 1/8 or 1/4-inch connector, particularly when it comes to contractor or consumer gear. However, depending on the age of a tool or where it was manufactured, the size may not conform to these standards.

The best way to measure a port opening to determine its size, is to measure the diameter of the opening in inches, right across the center of the port. With an accurate measurement you will know the pipe size and you’ll be able to get the right new connector or replacement part.

Making Sure You Have a Strong Seal When Connecting a New Fitting

Whether you’re replacing a fitting between a compressor and an air tank, or a fitting on a tool handle, you’ll need to ensure that you not only use the right size thread, but also that you create a strong seal when attaching the hardware.

The best way to achieve an airtight seal is to introduce Teflon tape into the thread.

Even when parts are manufactured to exacting standards that adhere to the NPT chart, there’s still potential for air to escape from a fitting. Teflon tape will help to create a tighter seal, which should retain its integrity throughout the lifetime of the fitting.

While Teflon tape can perform its job effectively, it is important to take care when wrapping any connectors.

The tape should be just sufficient to cover the male thread on a connector, and it should not overlap the end of the connector.

Avoiding any excess tape that extends beyond the end of the thread is quite important. High air pressure could cause this excess tap to become dislodged, and it could create blockages further along a hose, within other connectors, or inside an air tool.

Even if not dislodged, excess tape could cause a blockage or partial blockage that reduces the efficiency and total airflow of your compressor.

By carefully wrapping the male thread only, and ensuring that there is no overlap or excess, you can ensure that the tape will be compressed when connected to a female coupling, and there will be no chance of blockages.

There are numerous Teflon tape products available, and one of the most popular is this Dixon Valve sealant tape, which is affordable and the bestselling airtight sealant tape for air compressor fitting types.

Do Couplings Come With Teflon Tape?

While you might be able to find air fitting types that come packaged with Teflon tape, it is also becoming more common for ready-made equipment to have a type of sealant already within the connected pieces. Instead of tape, manufacturers use a type of paste or putty that creates a perfect seal between connectors.

While you won’t find this when looking for loose air compressor fitting types, you may find a sealing substance to be in major fittings on portable air compressors from leading brands.

If you are replacing equipment and come across any sealant paste, make sure that you clean off the excess before reapplying fresh Teflon tape. Just like tape, loose paste in the system can cause blockages in fittings, hoses, and air tools.

Alternatively, it is possible to use liquid pipe thread sealant on your own couplings, and there are plenty of good products available, such as this Rectorseal slow drying pipe sealant.

Common Coupling Products That Conform to the NPT Size Chart

With contractor and DIY air compressor accessories, the most common couplings will be elbow and straight fittings.

Some of these may use quick connect couplings (i.e. a hose or tool that doesn’t have a thread), but the main connection points will always use a threaded fitting.

Remember to use the NPT size chart and measure your air ports if you’re unsure about size, or simply refer to manufacturer documentation to know what kind of air hose fitting sizes you will require.

One of the best ways to get the couplings you need, is to invest in a package of spare parts. EPAuto manufacturers a useful set of couplings and quick connector parts, which are available in a 17 piece air compressor coupling pack that conforms to the 1/4-inch NPT size chart measurements.

Manufacturers also produce coupling sets for their own equipment, which can mean that you won’t need to worry too much about the NPT sizes, providing you cross check the product with your own model.

One example is the Campbell Hausfeld 17 Piece tool and accessory coupling kit, which will work on their own compressors and tools, as well as other equipment that uses NPT 1/4 inch connections.

Take Your Time to Find the Right Equipment

Now that you’re familiar with the NPT size chart, why it matters, and how it relates to the accessories and fittings that you can buy for your air compressor, you’ll find it much easier to choose the right products for repairs and upgrade projects.

Remember to always take your time to select a fitting with the right measurements, consult your manufacturer documentation if you get stuck, and always remember to create a good seal using either Teflon tape or a liquid sealant when making permanent connections.

Attention to detail will mean a more efficient tool that performs just as the manufacturer intended.

If you want to become more knowledgeable as far as air compressors are concerned, please feel free to browse through our buying advice section.

Also, if you are interested in buying a new air compressor, you can look through our wide selection of air compressor reviews to find the best one which will fit your budget and needs.

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Air Hose Fittings: All You Need To Know To Operate Your Air Compressor
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Air Hose Fittings: All You Need To Know To Operate Your Air Compressor
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If you own an air compressor and you need to replace air hose fittings,then air compressor hose fitting types and sizes will be one of your major concerns.Read all about it!
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