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What is the minimum velocity required for any building drain?

  1. 1 ft. / sec.

  2. 2 ft. / sec.

  3. 3 ft. / sec.

  4. 4 ft. / sec.

The correct answer is: 2 ft. / sec.

The minimum velocity required for any building drain is essential to ensure proper drainage and avoid issues such as clogging and water stagnation. A velocity of 2 feet per second is sufficient to transport waste and debris effectively through the plumbing system. This rate allows for a self-cleansing action within the pipes, helping to prevent sediment buildup and ensuring that the waste flows smoothly through the drainage system. Selecting a velocity that is too low can lead to problems, such as reduced flow and increased chances of blockages, whereas higher velocities can cause noise issues, potential damage to the piping system, and increased wear on fixtures. Therefore, adhering to the established minimum of 2 feet per second balances efficiency and system integrity, making it the correct answer.