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What is the size of a cleanout for 4 inch and greater piping?

  1. 2" (50mm)

  2. 3" (75mm)

  3. 4" (100mm)

  4. Same size as the pipe

The correct answer is: 4" (100mm)

A cleanout is a pipe fitting that provides access to a plumbing or drainage system for the purpose of cleaning or clearing blockages. For pipes that are 4 inches or larger, the standard size for a cleanout is 4 inches (100mm). This allows enough space for proper cleaning and maintenance of the system. Options A and B are too small and would require an adapter to be installed, while option D is incorrect as the cleanout should be the same size as the pipe for effective access.