The use of fittings is common in the plumbing industry. They help connect pipes and hoses securely. Fittings come in different types and shapes, each with its own mechanism. Two common fitting types are MIP and NPT. These two fitting types share common differences, leading to a debate over MIP vs NPT fittings.
Both of these fittings are useful, but in different conditions. For example, MIP fittings are best suited for easy-to-install plumbing applications. On the other hand, NPT fittings are more advanced, ideal for high-pressure applications. In this article, I will discuss all the fundamental differences between these two fittings. Let’s get started.
Basics of MIP and NPT Fittings
Let’s start from scratch – both MIP and NPT are types of threaded fittings. This means they have a thread that screws into other corresponding parts or pipes. MIP stands for Male Iron Pipe. On the other hand, NPT represents the National Pipe Thread.
MIP fittings have straight threads along their length. These straight threads with a consistent diameter along their length ensure easy installation. Conversely, NPT fittings have threads whose diameter decreases along their length. The taper design ensures tight sealing and is ideal for high-pressure applications. Both of these fitting types are widely used in pipelines.
Threaded fittings simply mean they have grooves. These grooves are useful in screwing them onto another part. For example, MIP fittings have grooves or threads on the external side. They are generally screwed on the female fitting, which has internal threads. This exterior thread on MIP helps in strong connections with the corresponding female fitting.
NPT fittings are considered more advanced than MIP fittings. Why? The reason is that these fittings make strong connections with other components. These connections create a strong seal, preventing leakage. This strong sealing is due to their taper design, or narrowing along their length. There is confusion among people about whether NPT requires a sealant when using pipelines.
This is wrong; both MIP and NPT fittings require sealant, i.e., Teflon tape. This tape removes all the tiny or microscopic gaps, making these fittings more secure. The primary difference between MIP and NPT lies in their shape and design. This design variation creates all other differences in their function, performance, and longevity. Both fittings (MIP and NPT) come in different sizes, indicating their versatility.
Differences Between MIP vs NPT Fittings
Fittings are a must-have in the plumbing industry. Without them, plumbers cannot assemble long pipelines. They use both MIP and NPT fittings where they need to ensure a smooth flow of fluid or gases. Below is the section where I will discuss the key differences between these fittings. Understanding these differences between MIP and NPT will help you determine which fit-in is best for what.
1- Function & Design
Both MIP and NPT fittings have primarily the same function. They both connect different pipes or other components. However, their effectiveness varies, making them suitable for different use cases. Interestingly, their design and shape influence their working and functionality. MIP fittings have a simple design with a thread going along the length.
The size or diameter of these threads remains the same and straight along the length. This makes them easier to use and fit, and they get screwed easily on the corresponding parts. However, this fitting is used when a small or micro-level leakage is acceptable. On the other hand, NPT fittings have a tapered design. This means their thread diameter decreases along its length.
These decreased diameters make them slightly thinner along the length. This narrow shape makes it tighten the corresponding part or components. The threads of the two parts fit together perfectly, resulting in an air-tight connection. No gas or liquid can leak, even at the micro level. NPT fittings are used when a high-sealing or leak-proof system is required.
2- Thread Type & Size
MIP fittings have external threads, also called male threads. As a result, MIP threads are compatible with FIP. The size of the threads or grooves remains the same across the entire surface of these fittings. On the other hand, NPT does not indicate thread types, as it indicates a standard thread. NPT can be of two types: MPT (Male NPT) and FPT (Female NPT).
In MPT, the threads are present on the outer surface. In FPT, the threads are on the internal sides, which is known as female NPT. The thread size in these fittings decreases along their length. It is worth noting that MIP and MPT both have external threads. In contrast, FIP (Female Iron Pipe) and FPT have the same internal thread.
3- Sealing Mechanism & Pressure Ratings
MIP fittings have threads on the external sides. These male threads are screwed into the corresponding female part. However, the thread connection does not provide any specific leak-proofing. Therefore, a separate sealant such as PTFE tape is used to prevent leakage. Additionally, the pressure rating of MIP fittings is lower. This means these fittings can withstand only moderate pressure from fluids or gases.
In contrast, NPT fittings have a taper design. Their threads have a reduced diameter along the length. This narrow shape allows the fitting screw to fit into the corresponding part more tightly. This tight connection ensures no leakage. These fittings use sealant, which further strengthens them and makes them leak-resistant. Due to better sealing, these fittings are used in high-pressure applications. Their pressure rating ensures they can handle pressure with ease.
4- Versatility & Sealant Requirement
MIP fitting is less versatile and requires sealant for leak-proofing and strong sealing. Remember, MIP fittings also indicate one thing: the thread type. This fitting uses male (external) threads. On the other hand, NPT fittings indicate two properties of the threads. First, it indicates the thread shape (taper design) and shows that the threads are narrowing along their length. Secondly, it also indicates the sizing of the threads.
NPT fittings can be used without sealant. Why? Their thread-size design (taper) makes their connection with the corresponding parts very strong. The chances of leakage become very low due to the tight connection. However, it is always recommended to use sealant (PTFE tape). This tape further improves sealing, making these fittings air-tight. For MIP fitting, using sealant is mandatory for a strong seal.
5- Materials & Durability
In terms of construction materials, both of these fittings are similar. The reason is that both MIP and NPT fittings can be made of either brass or stainless steel. Some MIPs also use carbon steel; however, stainless steel is the most common material for both types. You’ll also see NPT fittings made of PVC, but they’re not as strong as stainless steel fittings.
When it comes to durability, NPT fittings are a superior option. They last longer thanks to their better taper design, which provides excellent sealing. So fluid does not leak, resulting in better durability of these fittings. There is a chance of leakage in MIP fittings. This leakage is more likely when the fluid inside the pipe is under high pressure. Leakage can degrade the material, reducing the durability of MIP fittings.
6- Ease of Installation & Maintenance
MIP fitting is a better option if you prefer ease of installation. As I said above, the thread diameter remains the same throughout the length of these fittings. This ensures a straight design, which makes it easy to screw in other components. On the other hand, NPT has a tapered design, with the thread diameter decreasing along its length.
This narrow shape requires a more precise fit when you screw in other components. Small mistakes may result in an improper connection between two parts. MIP fittings require regular maintenance due to their tendency to leak. However, NPT fittings are leak-proof and more secure than MIP fittings. As a result, these fittings do not require regular maintenance, saving you hassle.
7- Leak Prevention & Compatibility
Leak prevention is a crucial factor one should consider when choosing a fitting. MIP is not ideal if you want a fitting with excellent leak resistance. The reason is their threads don’t fit tightly, resulting in smaller micro-level gaps. Fluids or gases can leak through these gaps despite the use of PTFE tape (sealant). Conversely, NPT fittings stand out for their leak-prevention performance.
Their threads are tapered, with a smaller diameter along their length. This narrow thread shape ensures smooth fits and proper tightening of the two components. This tight connection ensures no leakage even when high-pressure fluid is in the pipe. MIPs have external or male threads, and are compatible only with female threads. On the other hand, NPT offers greater versatility within a standardized system.
8- Cost & Common Applications (Use Cases)
MIP fittings are less expensive than NPT fittings. This is one of the primary reasons why it is preferred for simple plumbing. Although MIPs are cheaper, they are only suitable for low-pressure applications. When exposed to high pressure, these fittings can leak, which is a big drawback.
On the other hand, NPT fittings are expensive mainly because of their complex design and shape. However, these fittings are excellent for high-pressure applications. These fittings are used for heavy-duty applications due to their superior pressure-handling capabilities. Remember, both of these fittings require sealant, which can affect their prices.
Below is a table showing the common applications of MIP and NPT fittings
| Uses of MIP (Male Iron Pipe) | Uses of NPT (National Pipe Thread) |
| Plumbing connections | Industrial piping systems |
| Water supply lines | Gas distribution lines |
| Household pipe fittings | High-pressure hydraulic systems |
| Simple irrigation systems | Oil & petrochemical pipelines |
| Furniture/fixture connections | Manufacturing & processing plants |
Conclusion
Let’s conclude this article by noting that both MIP and NPT fittings are equally important. Which fitting you choose depends on your needs and requirements. If you prefer budget-friendly fittings that are easy to install, the MIP fitting is the best option. I highly recommend using sealant to ensure it resists leakage.
NPT fittings are suitable for high-pressure applications where leakproofing is the highest priority. These fittings have a tapered design that ensures a tight connection between the fitting and other components. This tight connection prevents leakage and performs better for longer durations. In this article, I have explained all the differences between these two threaded fittings.