In 4-inch pipe connectors, several types of threads may be used depending on the specific application and industry standards.

Here are some common types of threads found in 4-inch pipe connectors:

1. NPT (National Pipe Thread): NPT threads are the most common type of tapered thread used in pipe fittings in North America. These threads have a taper of 1:16, meaning the diameter increases or decreases by 1 inch per 16 inches of length. NPT threads are designed to create a tight seal when tightened, preventing leaks in the connection.

2. BSPT (British Standard Pipe Taper): BSPT threads are similar to NPT threads but follow British standards. 4 inch pipe connector  They also have a taper of 1:16 but are measured in metric units. BSPT threads are commonly used in Europe and other parts of the world.

3. BSPP (British Standard Pipe Parallel): BSPP threads are parallel threads that do not have a taper. Unlike NPT and BSPT threads, which create a seal through interference between the threads, BSPP threads rely on a sealing washer or O-ring to create a tight seal.

4. BSP (British Standard Pipe): BSP threads can refer to either BSPT or BSPP threads, as both are part of the British Standard Pipe thread family. BSP threads are widely used in plumbing and industrial applications in countries that follow British standards.

5. NPS (National Pipe Straight): NPS threads are straight threads that do not have a taper. Unlike NPT threads, which are tapered, NPS threads have a consistent diameter throughout their length. NPS threads are often used in applications where a leak-proof seal is not required, such as with certain types of couplings and flanges.

6. UN/UNF (Unified National/Unified National Fine): UN and UNF threads are standardized thread types used in various industries, including piping. These threads have a consistent diameter and pitch and are often used in specialized or high-pressure applications where precise thread engagement is required.

7. Metric Threads: In some cases, metric threads may be used in 4-inch pipe connectors, especially in regions where metric measurements are standard. Metric threads follow the International System of Units (SI) and are measured in millimeters.

It's essential to ensure that the threads on pipe connectors match those on the pipes being connected to avoid compatibility issues and leaks. Additionally, proper thread sealing techniques, such as using thread sealant tape or pipe joint compound, should be employed to create a reliable and leak-free connection.