How to Choose the Right Types of Coupling: A Checklist

For your fire hose to work properly, you need the right coupling fitting. A coupling is a connector that joins one length of hose to another. It can also be used to connect hose to a tap or other water source.

Firefighter setting up firehose

Coupling fittings are usually made of brass, stainless steel, or aluminum, and they come in many different sizes, thread standards, and genders. For the connection to work the way you want it to and not leak or fly off, you need to know exactly which pieces are compatible.

If your fire hose coupling parts are mismatched, it can lead to loss of money and time, not to mention frustration. Get exactly what you need by following this handy checklist.

Thread type

To begin the process of identifying the right coupling, begin with the thread type or thread standard. Each fitting uses a specific type, and each type has a different pitch and spacing to the threads, also known as threads per inch, or TPI.

National Standard Thread (NST) or National Hose (NH)

This is the most common thread type for fire hose. It may even be referred to simply as “fire hose thread,” because fire departments use this type the most. You’ll find this type of thread on many fire hydrants and accessories.

National Pipe Straight Hose (NPSH) or Iron Pipe Thread (IPT)

This is the second most common type of thread for fire hose. You’ll often find this straight thread on low-pressure water suction or discharge hose couplings.

National Pipe Tapered (NPT)

This is commonly used to connect hose to fixed piping systems, such as in plumbing and industrial use. We recommend using plumber’s tape when using connectors with this type of thread.

Other thread types

For fighting wildfires and other special uses, you may encounter Garden Hose Thread (GHT). You will also find specific fire hose threads for certain cities. The Fire Department of New York uses its own thread type which is different from the Chicago Fire Department or even Chicago Hose Thread.

Where to find it

To know which type of thread is used on an existing hose or coupling, check for a stamp with the initials of the thread type.

Once you’ve learned what type of thread you need, it’s time to decide which gender you require.

Thread gender

There are three basic genders for fire hose couplings: male, female, and ungendered.

Male couplings

Male couplings, hoses, and fittings have threads on the outside. You will typically find male couplings on equipment, such as fire hoses, which discharges water.

Female couplings

Female couplings have threads on the inside that allow them to receive a male coupling. You’ll often find female couplings on equipment that receives water.

Ungendered or ‘sexless’

There is a third gender for couplings that are neither male nor female. These fittings instead use  what’s called a Storz connection, which lets firefighters connect two parts using no threads at all. Storz uses a quarter-turn quick connection instead of threads.

Compatibility

Note that you may be able to combine different thread types and genders.

Thread type/genderCompatible with:
NH/NST maleNH/NST female
NH/NST femaleNH/NST male
NPT maleNPT female, NPTF female, NPTSH female
NPT femaleNPT male, NPTF
NPSH maleNPSH female, NPSM female
NPSH femaleNPSH male, NPT, NPTF, NPSM

Coupling size

Finally, once you’ve determined which thread type you need and what gender, you must make sure you have the proper size. Generally, sizes range from 3/4” to 6” in diameter.

How to determine your fitting size

You can find the size on the female coupling, or it may be printed on the fire hose itself.

If necessary, you can measure the diameter of the inside of the male coupling to determine the coupling dimensions.

We’re here to help

Now that you know just the piece of firehose coupling you need, it’s time to give Rawhide Firehose a call. Contact us for all of your firehose and fitting needs, including answers to any questions you may have about how to measure hose diameter or quick connect fittings. We’re happy to help you make sure you have the right fire hose coupling parts.

About The Author: Keith Eriksen

Keith was the president of Rawhide Fire Hose from 2000 thru 2018. He is a former member of the Wooster Township Fire Department, serving with the Wayne County Underwater Search and Rescue unit. He has extensive knowledge of valves and hydraulics from years of experience in the oil and natural gas production business. In addition to being an avid scuba diver with master diver endorsements he is also an instrument rated private pilot, certified for high performance and complex aircraft. He enjoys landscape and gardening work, gourmet cooking, spending time with his (grown) children and traveling with his wife, Vicki.

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