GHT and NPT are two types of threading systems used for connecting pipes and fittings in plumbing and mechanical systems. It is common for people to confuse these two systems because they are both used for similar applications and have similar thread profiles.
However, they are not compatible with each other due to differences in their thread dimensions and pitch. An adapter would be needed.
Today we’ll discuss GHT and NPT in great detail!
Why Are There Different Threads?
There are many different types of threading systems in use today, each designed for specific purposes and applications. Different thread systems are used for various reasons, including the type of material being connected, the pressure and temperature ratings of the system, and the geographic location where the system will be used.
One reason for the existence of different thread systems is the fact that different countries and regions have their own standards and regulations for pipe and fitting connections.
For example, the National Pipe Thread (NPT) system is widely used in the United States, while the British Standard Pipe thread (BSP) is commonly used in the United Kingdom and other parts of Europe. These different systems are not interchangeable due to differences in their thread dimensions and pitch.
Another reason for the existence of different thread systems is the need for threads that are optimized for specific materials and applications.
To illustrate this, some thread systems are designed for use with softer materials such as brass or aluminum, while others are designed for use with harder materials such as steel or stainless steel. Different thread systems may also be used in high-pressure or high-temperature applications to ensure a secure and reliable connection.
In short, different thread systems exist due to a combination of regional standards and the need for threads optimized for specific materials and applications.
Pipe Threads at a High Level
Here is a table of common pipe thread systems, along with their acronyms, full names, and general uses:
| FHT* | Female Hose Thread | Low-Pressure Applications |
| MHT* | Male Hose Thread | Low-Pressure Applications |
| BSP | British Standard Pipe | UK and Europe Plumbing |
| NPT | National Pipe Thread | United States Plumbing |
| MIP | Male Iron pipe | Steel Fittings & Pipes |
| Compression | Compression Threading | High-Pressure Applications |
Other common pipe thread systems include NPS (National Pipe Straight), NPSF (National Pipe Straight Fuel), NPSM (National Pipe Straight Mechanical), and BSPT (British Standard Pipe Taper). These thread systems are used for a variety of applications and are available in a range of sizes and pitches.
GHT vs. NPT Use Cases
GHT (Garden Hose Thread) is a type of thread commonly used for garden hoses and other low-pressure applications. This thread system is designed for use with softer materials such as brass or aluminum, and is not suitable for use in high-pressure or high-temperature systems.
GHT is often used for connecting garden hoses to spigots, hose fittings, and other low-pressure plumbing systems. It is a commonly used thread system in the United States, and is often found on hose bibs, hose splitter valves, and other outdoor plumbing fixtures. GHT is not intended for use with pipes, as it is not designed to withstand the higher pressures and temperatures that are often present in piping systems.
NPT (National Pipe Thread) is a more versatile thread system that is commonly used for pipes and fittings in the United States. It has a tapered thread design but a different pitch than GHT. NPT is suitable for use with a wide range of materials, including steel and stainless steel, and can be used in high-pressure and high-temperature systems.
NPT is often used for connecting pipes and fittings in plumbing, mechanical, and industrial systems. It is a widely used thread system in the United States, and is often found in residential, commercial, and industrial piping systems. NPT is suitable for use with a variety of materials, including brass, copper, steel, and stainless steel, and is capable of withstanding high pressures and temperatures.
In summary, GHT is generally used for low-pressure applications with softer materials, such as garden hoses and hose fittings, while NPT is more versatile and suitable for use in a wider range of applications, including high-pressure and high-temperature piping systems. It is important to choose the appropriate thread system for a given application to ensure a secure and leak-free connection.
GHT & NPT: Dimensions, Availability, Installation, Pros & Cons
GHT and NPT are both standardized thread types that are commonly used in piping systems. They are primarily used to connect pipes and fittings, and they have a number of advantages and disadvantages that make them suitable for different applications.
GHT Specifications
GHT, or Garden Hose Thread, is a type of thread that is commonly used in hose connections in the United States. It is defined by ANSI/ASME B1.20.1, and it has a unique thread form that is designed to create a leak-proof seal when used with a gasket or O-ring. GHT has a 3/4-inch nominal diameter and a 11.5 TPI (threads per inch) thread pitch. It is typically made from brass or other corrosion-resistant materials, and it is designed to be used with hoses that have an inner diameter of approximately 5/8 inch.
NPT Specifications
NPT, or National Pipe Thread, is another type of thread that is commonly used in the United States and other countries. It is defined by ANSI/ASME B1.20.1, and it has a tapered thread form that is designed to create a leak-proof seal when used with a sealant or tape.
NPT has a wide range of sizes, with nominal diameters ranging from 1/16 inch to 4 inches and a TPI thread pitch ranging from 8 to 18. It is typically made from carbon steel or stainless steel, and it is designed to be used with pipes that have a nominal diameter that is equal to or larger than the NPT thread size.
GHT Advantages & Disadvantages
One of the main advantages of GHT is that it is relatively easy to use, as it only requires a wrench or pliers to connect. As you probably know, if you have a good garden hose, you can just use your hands to connect it to a spigot.
It is also relatively inexpensive, with prices ranging from a few cents to a few dollars per fitting. However, it has a limited range of sizes and is not suitable for high-pressure or high-temperature applications.
NPT Advantages & Disadvantages
NPT, on the other hand, has a wider range of sizes and is suitable for high-pressure and high-temperature applications. It is also relatively easy to use, as it only requires a wrench or pipe threader to connect. However, it is more expensive than GHT, with prices ranging from a few dollars to several hundred dollars per fitting. It also requires the use of a sealant or tape to create a leak-proof seal, which can be time-consuming and messy.
Both GHT and NPT are standard in the United States and are used in a wide range of applications, including irrigation, water supply, and industrial piping systems. They are also used in other countries, although other thread types may be more common in some regions. In general, GHT is suitable for low-pressure and low-temperature applications, while NPT is more suitable for high-pressure and high-temperature applications.
How to Measure the Size of a Pipe or Hose
There are several methods that you can use to measure the size of a pipe or hose, and the most accurate method will depend on the type of material and the size of the pipe or hose.
Pipes
Tape Measure or Ruler
One common method for measuring the size of a pipe is to use a tape measure or ruler to measure the outside diameter (OD) of the pipe. This will give you the nominal size of the pipe, which is a standardized size that is used to identify the pipe. You can then use a pipe size chart to determine the actual size of the pipe based on the nominal size and the schedule (wall thickness) of the pipe.
Index Card or String
Another method for measuring the size of a pipe is to use an index card or a piece of string. To do this, you will need to wrap the index card or string around the pipe and mark the point where the ends meet. You can then measure the length of the index card or string to determine the circumference of the pipe, and divide this by pi (3.14) to get the diameter of the pipe.
Hoses
Tape Measure or Ruler
For hoses, you can use a tape measure or ruler to measure the inside diameter (ID) of the hose, which is how garden hose sizes are measured. This will give you the actual size of the hose, which is typically expressed in inches. Sometimes in millimeters.
Index Card or Piece of Paper
Again you can roll up an index card and insert it into the hose where it meets the rubber. Remove the index card and measure the diameter size (end to end) of the hole at the end of the index card. This will give you your garden hose size.
It is important to note that these methods may not be accurate for all types of pipes and hoses, and you may need to use more specialized tools or techniques to get an accurate measurement. For example, you may need to use a caliper or micrometer to measure the size of a pipe or hose that has a small diameter or a thin wall thickness. You may also need to consider other factors, such as the type of material and the condition of the pipe or hose when determining the size.
How to Easily Determine What Threads You Have
There are a few ways to determine if a pipe or fitting has NPT threads.
Use a Pich Gauge or a Caliper
One of the most straightforward methods is to measure the thread pitch (the distance between threads) using a thread pitch gauge or a caliper. NPT has a fixed thread pitch of either 8, 11.5, or 14 TPI (threads per inch), depending on the size of the pipe. If the thread pitch matches one of these values, it is likely that the pipe or fitting has NPT threads.
Examine the Shape of the Threads
Another method is to examine the shape of the threads. NPT has a tapered thread form, which means that the diameter of the threads decreases as you move away from the end of the pipe. This creates a seal when the threads are tightened together, and it is a distinctive feature of NPT threads. If you see this tapered thread form, it is likely that the pipe or fitting has NPT threads.
Screw Test
You can also try screwing a pipe or fitting with NPT threads onto the pipe or fitting in question. If the threads match and the connection is tight and secure, it is likely that the pipe or fitting has NPT threads.
Pipe Thread Chart or Plumbing Supply Store
If you are still unsure, you can consult a pipe thread chart or a plumbing supply store to determine the thread type. You may also need to consider other factors, such as the size of the pipe or fitting and the type of material, to accurately identify the thread type.
Final Thoughts
In conclusion, both NPT and GHT have their own advantages and disadvantages, and the choice between the two will depend on the specific needs of your piping system.
NPT is a widely used thread type that is suitable for high-pressure and high-temperature applications. It has a wide range of sizes and a tapered thread form that creates a leak-proof seal when tightened. However, it is more expensive than GHT and requires the use of a sealant or tape to create a leak-proof seal.
GHT, on the other hand, is a less commonly used thread type that is primarily used for low-pressure hose connections. It is relatively easy to use and inexpensive, but it has a limited range of sizes and is only suitable for low-pressure and low-temperature applications.
Overall, NPT is a more versatile and durable thread type that is suitable for a wide range of applications. However, if you have a specific need for a low-pressure hose connection, GHT may be a suitable alternative.