ISO 228-1 is an international standard for pipe threads, specifically defining parallel (straight) thread profiles used in mechanical connections. These threads typically do not seal on the threads themselves; instead, sealing is achieved using external elements such as gaskets or O-rings.

Key Features:

• Thread type: Parallel (straight) — not tapered
• Thread profile: 55° Whitworth form
• Scope: Specifies dimensions, tolerances, and marking rules for internal and external pipe threads
• Sealing: Achieved on the mating surface, not between the threads (e.g., flat face + gasket)
• Applications: Commonly used in plumbing, pneumatic systems, and low-pressure gas lines
  
  

Purpose and Benefits:

• Widely used in European and international piping systems
• Suitable for applications requiring sealing with a gasket or sealing ring
• Should not be confused with ISO 7-1, which defines tapered threads and uses a different sealing principle