What You Need  to Know between Npt vs. Ips

NPT and IPS threads vary, and you need to understand the differences whenever you require a fitting. Therefore, developing some simple differences between the two is necessary when it comes to fittings. Unfortunately, one of them is the old system while the other one is a new model.

Therefore if you want to know how these two fittings differ, we are here to provide you with every piece of information. Furthermore, the article shall touch on various aspects that can point out the differences between NPS and IPS fitting. What you need to do is, therefore, rely on our article for educating information.

At the end of the discussion, we hope you can draw clear differences between the two fittings and then understand when they are compatible. These two fittings determine the piping you would install in your house. Stay tuned for juicy information. Besides, we shall show you how the two threats work.

What you need to know between NPT vs IPS

1. What is IPS?npt vs ips

Based on the Google definition, we can say that IPS is simply Iron Pipe straight threading. This type of fitting is mainly designed to seal a particular washer-shaped gasket. It works just like your toilet’s hose thread. This system of threading emerged before World War II.

It categorizes the pipe walls’ thickness utilized by many manufacturers of polyvinyl chloride, iron, piping, and PVC that joins the faucets. They are therefore suitable for both business and home applications.

Another name for IPS is NPSH, having close actual diameters like those in NPT. IPS pipes are mainly used in schedule 80 or 40 plumbing iron pipes. Schedule 80 tends to be stronger and bigger compared to PIP, i.e., Plastic Irrigation Pipe. This is a standard size that is mainly utilized in the agricultural sector today. For instance, IPS faucets may be used in both outdoor and indoor applications.

2. What is NPT?What is NPT

This abbreviation means National Pipe Tapered threading. It is also famous for ASME/ANSI pipe threads. It is a traditional type of fitting that was used mainly in the US AND UK. However, the style diminished after World War II, when the IPS fittings were introduced.

This body is responsible for taking measurements of tapered threads on fittings or threaded pipes. NPT is not similar to a straight bolt thread because the tapered thread can pull tight, achieving a closer seal.

How to connect NPT threadsHow to connect NPT threads

Tightening NPT fittings is not that complicated but involves simple instructions. But before you do anything, you should understand that there are female and male threads whereby the female one features threads on its internal part while the male has threads on its outer part. Follow these steps;

  • Fix the female into the male fitting
  • Rotate the male one in a clockwise motion.
  • Continue rotating the male pipe until it reaches the end. You may require to do maybe up to four complete revolutions. However, this is based on the type or size of the fitting.

NPT Vs. IPS Treads: Comparison table



National Pipe Tapered (NPT) Iron Pipe straight (IPS)
¾” 1.050 14 1.035 14
1” 1.315 11.5 1.295 11.5
1 ½” 1.900 11.5 1.878 11.5
2” 2.375 11.5 2.352 11.5
2 ½” 2.875 8 2.841 8
3” 3.500 8 3.470 8
3 ½” 4.000 8 3.970 8
4” 4.500 8 4.470 8
4 ½” 5.000 8 4.970 8
5” 5.563 8   – 8
6” 6.625 8 8

From the table above, you can realize that the real OD is close. On the other hand, the threads per inch alias TPI are similar. This implies that NPT and IPS have close similarities. Now, does this mean that you can use the NPT and IPS together? In simple words, are NPT and IPS compatible?

No, it is impossible. But this comparison means that you can achieve a helpful mechanical lock against the two components on rare occasions. A good example is when a faucet with NPT shanks drops beneath the water supply sink attachment. You can use untapered nuts to secure this on the sink.

Key points that I thought you should knowKey points that I thought you should know

There are stainless steel and brass fittings on the market whereby each of them is designed for specific fittings. Brass is mainly designed for copper tubing, while stainless steel is for stainless steel tubing. This means that when you fit brass into steel tubing, the brass tubing won’t withstand the force because it’s not suitable for the ferrule. As a result, it may not drive into the steel tubing easily.

Therefore, you may not achieve a perfect seal. Additionally, connecting the two tubings may cause galvanic corrosion.

You may meet either NPT tapered thread ends or compression. Compression is mainly designed for tubes with specific OD (outer diameter). Whenever a nut with ferrules is forced into a certain tubing, it will compress to develop a seal.

NPT ends differ from compression ends, whereby the NPT doesn’t feature ferrules nor nuts but depends on the threat connection. In addition, NPT product designation relies on ID (Internal Diameter) like in plastic tubing but not OD like in compression.

The metallic ferrules in compression ends may be substituted with ferrules from different materials. For instance, if you try to join any fitting to a ¼-inch Outer diameter glass tube, try replacing the ferrules with a weaker material such as graphite.

NPT fittings can either be found as female or male. It would help if you understood that there are female and male threads whereby the female one features threads on its internal part while the male has threads on its exterior part.


  • What is the meaning of CTS in plumbing?

CTS abbreviation stands for Copper Tube Size. It determines the female end valve connection where the copper fitting is placed and connected using capillary action. This is simply sweating, compression or sweating.

  • What is the meaning of ½” IPS?

In most cases, ½” IPS implies Iron Pipe sizing. It doesn’t refer to the Iron Pipe straight. It doesn’t matter whether the threading is straight like faucets or not; we refer to it as IPS (Iron Pipe Size).

  • Can female pipe threads taper?

NPT are tapered Pipe thread standards. Female and male tapered pipe threads connect themselves but will require a sealant to prevent leakage. Sealants are necessary as they fill available voids between threads that may move around the spiral.

  • Can I recycle my NPT fittings?

Absolutely no, the action is highly discouraged and should not be done with National Pipe Tapered fittings. Over-tightening is normal, mostly when a certain fitting is recycled. This means that reusing the fitting may give rise to leakage or galling.

 Final words

To wind up on what we have discussed above, you need to know that these fittings vary slightly. The sizing plays a vital role when establishing the differences, which we have offered you above. Go through the comparison and see the comparisons and differences. As much as the sizing is not similar, the TPI (Threads Per Inch) is similar.

If you are a plumber, the sizing and knowing the type of tubing you require is inevitable based on your area of specialization? How I wish you could have gone through the entire article to scoop everything. The article has covered essential information concerning the NPT and IPS threads.

Leave a Comment