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Thread Guide

Learn more about the different types of thread and how they connect.

When it comes to the different hose and pipe threads available, it can get confusing. We have put together an easy to follow guide to help you determine which thread type will suit your applications and what each acronym means.


These are the basic acronyms used when referring to different thread types:

  • F - Female - Goes on the outside around a ‘Male’ thread.

  • M - Male - Goes on the inside of a ‘Female’ thread.

  • NH / NHT / NST - (National Hose / National Hose Thread / National Standard Thread) - These are 3 common acronyms for the same thread type. This is the most popular hose thread in the United States.

  • NPSH / IPT - (National Pipe Straight Hose / Iron Pipe Thread) - These are both the same thread type and common with regular straight pipe.

  • NPT - (National Pipe Thread Tapered) - This is a tapered pipe thread. Commonly found with plumbing applications where the connection is permanent.

  • GHT - (Garden Hose Thread) - The standard garden hose thread. Commonly 3/4".

NH / NHT / NST

When it comes to NH, NHT, or NST thread, it's often referred to as ‘fire hose thread’. This style of thread is straight meaning it is the same dimension at the start of the thread as it is at the end.

How this type of thread seals to eliminate any water leak is by using a rubber washer seal in the ‘female’ coupling which the male thread compresses against to create a watertight seal.

With fire hydrant thread type and size, it can vary depending on the area but most of the time fire hydrants use an NST thread and have 2.5” and 4.5” outlet ports.


Compatibility:

  • Male NH (NST) - Female NH (NST)

  • Female NH (NST) - Male NH (NST)

Not compatible with other thread types.


NPSH

NPSH thread is most commonly referred to as ‘standard pipe thread’. This again, like the NST thread, is also straight but has more threads per square inch (TPI) as seen in the diagram.

This type of thread also seals the same way the NST thread with a rubber washer in the ‘female’ coupling which the ‘male’ coupling compresses against.

NPSH thread is commonly used in applications like water suction pipes and discharge hose couplings.

Compatibility:

  • Male NPSH - Female NPSH

  • Female NPSH - Male NPSH or NPT


NPT

NPT thread is commonly known as ‘pipe thread’ and not found with discharge and suction hoses but instead used in plumbing/piping applications where the connection is permanent. NPT has the same number of threads per square inch (TPI) as NPSH but the threads are tapered.

Unlike the NST and NPSH threads, this type of thread does not normally use a rubber washer in the ‘female’ coupling to seal, but instead, the tapered thread creates its own seal.

It's always recommended to use a thread tape (PTFE Tape) with NPT to ensure the seal is leakproof.

Compatibility:

  • Male NPT - Female NPT or NPSH

  • Female NPT - Male NPT


GHT

GHT is also referred to as ‘garden hose thread’ which is what most would be used to and would currently use around their garden or property but also used by wildland fire crews when water is in short supply.

This type of thread seals with a rubber washer just like NST and NPSH. Common hose sizes (inside diameter) for this type of thread are ⅝” and ¾” and with both other these, the standard garden hose thread size will be the same GHT thread.

If you are needing to connect a larger hose to a GHT ‘male’ thread outlet, you can use a garden hose thread adapter.

Compatibility:

  • Male GHT - Female GHT

  • Female GHT - Male GHT

Not compatible with other thread types.


Thread Adapters and Couplings

Sometimes in certain applications, you are faced with trying to connect two different threads or sizes together. It's impossible and totally impractical to have hoses, nozzles, etc. in each thread type and size available in order to be prepared for any situation. This is why Alpine offers a large selection of thread adapters. These adapters allow you to connect different thread types and sizes very quickly. This allows you to use 1 size and type of hose, for example, and be able to connect to multiple different nozzles, and water sources (e.g. water pump or fire hydrant).

Fire hose thread adapters are very common with fire crews for this very reason.

Alpine thread adapters are made in the USA and built to last.

If you have any further questions about thread types or need helping finding the right thread for your needs, please don't hesitate to reach out. CONTACT US


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