What is the difference between BSPT and BSPP threads? This is the first question that comes to mind when you work with pipes, valves, hydraulic equipment, or other fluid systems. Many beginners consider them the same, as both belong to the British Standard Pipe (BSP) family. Both of them are used to connect pipes and fittings securely. However, in reality, BSPT and BSPP do not seal in the same way. This is what makes their usability, reliability, and design different. But that’s not all. In this guide, I will discuss the key differences that set these thread types apart. So let’s get started.
Key Differences Between BSPT and BSPP Threads
No doubt, both BSPT and BSPP belong to the BSP thread family. However, they are designed for different sealing approaches. So, what really makes BSPT different from BSPP? Let’s compare head-to-head BSPT and BSPP to see where they really differ.
1- Name Meaning, Thread Shape & Design
The first major difference is clear from the names themselves. BSPT means British Standard Pipe Taper. However, BSPP means British Standard Pipe Parallel. The words “Taper” and “Parallel” are what actually tell us about their design. The thread shape in BSPT is tapered. Its diameter gradually becomes smaller toward the end. This gives the fitting a slightly cone-like shape. On the flip side, the thread shape in BSPP is parallel, so the diameter remains constant along the threaded section.
2- Tapered & Parallel Profile
The profile refers to the shape of the threaded part along the fitting. In a BSPP thread, the profile is parallel. It means the threaded section keeps the same diameter from one end to the other. It does not become narrower as you screw it in. These threads help connect and hold the two parts together.
On the other hand, the profile in BSPT is tapered. In other words, it has a slightly cone-shaped profile. So, the threaded section becomes slightly narrower toward the end. The male thread has a larger diameter at the beginning and a smaller diameter near the tip.
3- Sealing Method & Performance
Another thing that highly differentiates the BSPP and BSPT is their sealing method. There is no doubt both create secure connections. However, a BSPT thread uses the threads themselves to help create the seal. The thread is tapered. So when you screw the male and female threads together, they tighten and create pressure between them. This pressure between the threads helps close small gaps.
In contrast, the BSPP thread does not normally seal through the threads. Here, the thread is parallel. That’s why it doesn’t get tighter as it moves into the fitting. So, in this case, you will need a separate sealing part, such as an O-ring, bonded washer, or gasket, which is usually compressed between the two surfaces.
4- Thread Diameter & Structure
The thread is the width of the threaded part of a fitting. The arrangement of this diameter is another difference between BSPT and BSPP. For example, in a BSPP thread, the diameter remains the same along the threaded section. The thread is parallel, so it does not become narrower toward the end. This diameter does not create pressure between the threads. However, in a BSPT thread, the diameter is not the same from one end to the other. The diameter gradually becomes smaller toward the end of the fitting. This is because of the tapered thread design. This change in diameter allows the male and female threads to tighten as you screw them together.
5- Installation & Tightening
Now, it comes to installation and tightening, which differ for BSPT and BSPP threads. With a BSPT thread, the fitting becomes tighter as you screw the male and female parts together. Why? Because the thread is tapered. As the fitting goes deeper, the threads press more firmly against each other. However, proper tightening is crucial; if you overtighten the threads, they can be damaged.
In contrast, with a BSPP thread, the threaded section stays the same diameter. Therefore, threads only help position and hold the fitting. An O-ring, washer, or gasket normally creates the seal. So, tightening mainly relies on these washers and gaskets.
6- Sealant Use & Requirements
The way each thread type prevents leakage also varies between BSPP and BSPT. If we discuss BSPP, there is no need for any sealant on the threads to create a tight seal. The sealing depends on the gasket, bonded washer, and O-rings. They don’t create any gaps that need extra sealant. On the flip side, a BSPT must use a sealant such as PTFE tape. The threads are tapered, so they press against each other as the fitting is tightened. But this sealing sometimes creates small gaps that must be filled. To fill these gaps, there is a need for sealant.
7- Leak Protection & Reliability
BSPT and BSPP both provide reliable connections to prevent leakage. However, they do this differently. A BSPT connection primarily relies on its tapered threads for leak protection. As you tighten the male fitting, its tapered threads press against the female threads. But still, there remain small gaps that sometimes cause leakage. To prevent this, additional sealant is needed. Conversely, a BSPP thread normally uses a separate sealing element, such as an O-ring. The parallel threads hold the fitting in position; at the same time, the sealing element creates the barrier against leakage. So it provides more reliable protection against leakage from the start.
8- Maintenance & Reusability
Maintenance needs are another area where BSPT and BSPP differentiate clearly. In this regard, BSPP often wins as it is easier to remove and reuse. The reason lies in its parallel thread design. When you remove the fitting, there is usually no need to remove thread sealant from the threads. Also, the repeated maintenance is convenient with these threads. If an O-ring becomes worn, you can replace it without relying on the threads to create the seal.
The threaded portion will remain usable as long as it is still in good condition. On the flip side, with a BSPT connection, the tapered threads become tighter. The threads themselves create the seal. Thread sealant or PTFE tape is also used. So, when you remove the fitting, the old sealant will remain on the threads. Before reinstalling the fitting, you will need to clean the threads and apply fresh sealant. All this makes its frequent maintenance and reusability difficult.
9- Applications & Best Use Cases
Due to variations across many aspects, the usability of both BSPP and BSPT differs. For instance, BSPT is used where a tapered pipe connection is suitable. You can often use a BSPT thread in:
- Gas piping systems
- Plumbing systems
- Compressed-air lines
- Industrial pipework
- Water hoses
- Fuel piping
- Some hydraulic systems
- General fluid connections
On the other hand, BSPP is widely used in equipment where a separate sealing element is preferred. It is used in:
- Hydraulic hoses
- Hydraulic valves
- Hydraulic pumps
- Hydraulic cylinders
- Pneumatic equipment
- Pressure gauges
- Industrial hoses
- Fluid-control equipment
10- Cost & Affordability
Lastly, there is an overall cost that varies between BSPP and BSPT threads. But remember, there is no fixed rule that one type is always cheaper than the other. The price can change depending on the fitting size, material, manufacturer, and design. However, most of the time, BSPP fittings may cost slightly more.
The reason is that they use an O-ring, bonded washer, or other sealing element. These parts need to be replaced during maintenance, increasing overall costs. However, the higher initial cost does not mean BSPP is more expensive overall. BSPT fittings are more affordable. Their tapered threads create the connection without needing a separate O-ring, washer, or gasket. But using extra sealant can sometimes add to the cost and the installation step.
BSPT vs BSPP: Which One Should You Choose?
There is no single best choice between BSPP and BSPT threads. The final choice depends on your system, sealing method, and equipment requirements.
Choose BSPT when the system is designed for tapered thread connections and thread-based sealing. It is slightly more affordable and offers more reliable sealing using a sealant. However, you should choose BSPP when the system is designed for parallel threads with an O-ring, washer, or gasket.
From the differences, you can see that each thread type varies in many aspects. These variations highly affect your choice. If you choose a thread that doesn’t match your system’s needs, the result will be unwanted leaks. So always match how your system is designed to connect and seal, and then choose the most reliable thread. For example, a BSPT thread has a tapered profile. So it becomes tighter as it is screwed in, providing a strong connection.
BSPT is also useful when a simple threaded connection is preferred. However, it needs the right sealant, which adds to the installation step. On the other hand, BSPP is often a practical choice when the equipment is designed for parallel threads. Its parallel threads hold the fitting, while a separate sealing element provides leak protection. This can make inspection, seal replacement, and repeated servicing easier.
Conclusion
BSPP and BSPT are the two most common types of threads. At first, they look alike because they are in the same family. That’s where many beginners get confused. To make things easier for you, I have discussed the key differences between them in this guide. For example, BSPT has tapered threads that become tighter as they go in. BSPP has parallel threads that stay the same size. The biggest point to remember is the sealing method. BSPT uses tight thread contact, often with thread sealant or PTFE tape. BSPP normally uses a separate O-ring, washer, or gasket to create the seal. This is why you cannot choose a fitting just because its threads seem to fit. No, the right choice always depends on the system. BSPT is a good fit for tapered pipe connections. BSPP is a better choice for equipment designed around separate seals.