Fire Hose Fittings: Couplings and Threading

Quick question: Do you know the differences between NH (NST), NPT, and NPSH (IPT) when it comes to fire hose threading?  

If you aren’t familiar with different types of fire hose fittings and couplings, knowing the differences between the initialisms can be pretty confusing. 

Not understanding these differences can lead to mismatched parts, which leads to loss of money and time—not to mention plenty of frustration. 

Many factors go into matching different fire hose components together. We’re here to clear up some of the mystery and give you some great resources to keep handy for when you do need to purchase and match the right fire hose products. 

The Basics of Fire Hose Fittings 

First, what are hose couplings?  

A hose coupling is a fire hose fitting that is located on the end of a hose. It couples, or connects, with a hose, tap, or water source, and is typically made of brass, stainless steel, or aluminum. 

The key characteristics to understand regarding proper thread attachment are size (3/4” to 6”), thread standard, and gender. Male coupling has threads on the outside, while female coupling has threads on the inside. When you have 2 fire hose fittings, you’ll need one to be male and one to be female. 

Some couplings are “sexless.” Storz, for example, is a quarter-turn quick connection. 

The easiest way to identify what type of thread you need is by looking at the couplings on the fire hose you want to replace. There should be a stamp with the initials of the thread type. A water source fitting/adapter may also have the stamp.  

If you need to know what to use on a fire hydrant, call the local fire department. There are also fire hose adapters that can be used to change from one size thread or thread pattern to another. 

If there’s no stamp available, you can carefully count the threads per inch and measure the outside diameter of the male coupling; however, this can be a very tricky procedure. 

Fire Hose Threads 

What initials should you use to identify the proper fire hose fitting threading? There are many threads out there, but three are used primarily:  

1. NH or NST 
2. NPT 
3. NPSH or IPT 

NH/NST Threads 

NH stands for National Hose and NST stands for National Standard Thread. This is often referred to as “fire hose thread” because fire departments use it the most. It’s popular on many fire hydrants and accessories.  

Garden hose thread (GHT) is also referred to as NH. 

Compatibility:  

• Male NH/NST to Female NH/NST 
• Female NH/NST to Male NH/NST 
• Because these are not compatible with other thread types, fire hose thread adapters are used to connect the different types of couplings. 

NPT Threads 

NPT stands for National Pipe Tapered and is mostly used in plumbing and industrial. It’s sometimes simply called pipe thread. 

It’s recommended to use plumber’s tape or thread-sealing paste. NPT is compatible with NPSM threads if you choose male NPT to female NPSM (see below), whereas NPT vs GHT is not compatible.  

Compatibility:  

• Male NPT to Female NPT, NPTF, NPSM, NPSH 
• Female NPT to Male NPT or NPTF 

NPSH/IPT Threads 

NPSH stands for National Pipe Straight Hose. IPT stands for Iron Pipe Thread. NPSH is a straight thread and is popular on low-pressure water suction and discharge hose couplings. 

Compatibility: 

• Male NPSH to Female NPSH, NPSM 
• Female NPSH or Male NPSH, NPT, NPTF and NPSM 

Fire Hose FAQs 

Still a little confused? Here are a few frequently asked questions.  

Q: What is a fire hose fitting called?  

A: Fire hose fittings are commonly called couplings. These are located on the end of a hose to connect with another hose, tap, or water source. 

Q: What are the different types of fire hose fittings?  

A: The different types are (1) NH or NST, (2) NPT, and (3) NPSH or IPT.  

Q: Is fire hose thread the same as NPT?  

A: NH or NHT threading is mostly used for fire hoses. NPT threading, which has the same number of threads per inch, can be used. However, since the threads do not taper, you can only create a non-permanent connection using a female-type coupling on an NPT fitting.  

Q: What are the differences between GHT vs. NPT?  

A: When it comes to garden hose thread vs. NPT, the main difference is that GHT has parallel thread that is used to connect garden hose fittings. NPT threads are tapered, and they’re used for plumbing and pipe fittings.  

Get High-Quality Fire Hose Fittings 

Knowing what goes into fire hose fitting threading and coupling might seem confusing at first, but knowing the basics and having some solid resources at your disposal takes the guesswork out of the process. 

At Rawhide, many of our fire hoses come with a standard thread pattern. However, other thread patterns may be available upon request.Need a custom threading or coupling solution? Rawhide Fire Hose can help you find the hose you need. 

View our fire hose products or start customizing your hose today.