What Thread Types Are Used in Stainless Steel Pipe Fittings

The Basics of Threaded SS Pipe Fittings

Threaded connections remain one of the most popular joining methods for stainless steel pipe fittings. These threads create tight mechanical seals by screwing matching male and female ends together. They are widely favored for small-bore piping, maintenance work and projects where welding or pressing is not practical. Different regions and industries adopt distinct thread standards, so matching thread type is critical to avoid assembly failures. IFAN produces stainless steel fittings with multiple standard thread options to meet global plumbing and heating project demands.

NPT Thread

NPT, or National Pipe Taper, is the dominant thread standard used across North America. It is a tapered thread, meaning the diameter gradually changes along the thread length. When tightened, the taper compresses the thread surface to form a seal. NPT threads are common in water, gas and low-pressure fluid piping. Users need thread seal tape or compound to fill tiny gaps and prevent leakage. One important note: NPT threads seal on the taper, not purely on thread metal contact.

BSP Thread Family

BSP stands for British Standard Pipe, widely used in Europe, Asia, Australia and many global markets. There are two main variants: BSPP parallel thread and BSPT tapered thread. BSPP has a constant thread diameter and relies on a gasket or face seal rather than thread contact. BSPT is tapered, similar in concept to NPT, and forms a seal by thread compression. Mixing BSPP and BSPT threads is not recommended, as they may screw together but cannot form a reliable leak-proof joint.

ISO and Other Common Thread Standards

ISO pipe threads follow specifications closely related to BSP standards and are often seen in industrial fluid systems. Some specialty stainless steel fittings also use metric threads for custom equipment connections. Metric threads are less common for standard plumbing pipes and mostly reserved for machinery connections. Always verify thread specification before ordering, because similar-looking threads may not interlock properly.

How to Select the Right Thread Type

Your thread choice mainly depends on the project location, existing pipe system and working pressure. NPT fits North American installations. BSPP and BSPT serve European and many international markets. Tapered threads work well for compact joints, while parallel threads offer easier repeated disassembly. Mismatched threads cause slow leaks or thread damage during installation. IFAN clearly marks thread types on product listings to help distributors and installers pick compatible stainless steel fittings quickly.

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