Will Be Working On Fire Hydrants? What Thread Size Means And 2 Types Of Adapter Threads Available

8 December 2018
 Categories: , Blog


If you will be working on fire hydrants you need to learn as much as you can about them. One thing you need to learn is the type of thread that is used for the fire hydrant adapter. To help you, below is some information about what thread size is as well as two types of adapter threads available.

Thread Size

Thread size is referring to thread pitch and threads per inch (TPI). You will find a variety of TPIs with different number of threads that will fit on fire hoses, nozzles, and adapters. You will hear the words male and female when learning about adapter threads. Female refers to internal threads and male refers to eternal threads. When the female and male adapters are threaded together this is known as mating. This generally means the two adapters are connected well together.

You will also hear the word "nipple," which refers to an adapter that has male threading on each end. You will hear the word "coupling" also, which refers to an adapter that has female threading on each end.

Types of Adapter Threads

There are different types of adapter threads available including the following.

National Pipe Tapered

National Pipe Tapered (NPT) adapter threads is commonly called a pipe thread. This is because the thread is tapered, which means the exterior diameter of the adapter narrows as it gets to the end of the adapter. This allows a female and male adapter to connected to the NPT. As the female and male fittings are connected, they make a tight seal. Because of this, no gaskets have to be used.

If this type of thread is used, you have to swivel the female coupling on the hose to make a good connection. One benefit of NPT adapters is they makes a tight seal on their own without having to add any type of sealant. This allows the adapter to hold up well under high pressure and high heat situations.

National Pipe Straight Hose Thread

Another type of thread is known as the National Pipe Straight Hose Thread (NPSH). This type of adapter has the same amount of threads as the NPT adapter, but the main difference is the threads do not taper. Female adapters that use NPSH threads will connect to metal pipes, PVC pipes, or any coupling that has NPT or NPSH threads. When the fittings are connected, they have to be sealed by a sealing agent, which is generally Teflon tape or cement. Once they are sealed, they can handle high pressure and high heat.  The male side of an NPSH thread will only connect to hoses, nozzles, or fittings that have NPSH threads. If you want to thread an NPSH to an NPT female, you must use a coupling that has NPSH threads to make a proper connection.

Do some research to learn about other thread types used on fire hydrant adapters. For more information, reach out to companies like Buy Wholesale Company