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What is the Drainage Fixture Unit (DFU) value for a lavatory?

  1. 1

  2. 2

  3. 3

  4. 4

The correct answer is: 2

The Drainage Fixture Unit (DFU) value for a lavatory is crucial for plumbing system design and helps to estimate the load that a fixture will impose on the drainage system. A DFU value of 1 is typically assigned to a lavatory. In plumbing codes, lavatories are generally considered to have a moderate flow rate and usage, reflecting their function in a residential or commercial setting. Assigning a DFU value of 1 allows plumbers to calculate the total drainage load more accurately, ensuring that the plumbing system can handle the expected peak flow under normal usage conditions. This DFU value is essential when sizing drainage pipes and determining venting requirements. Calculating the DFU for various fixtures helps ensure compliance with plumbing codes and prevents future drainage issues. Understanding the significance of the DFU value assists plumbers in effective system design and installation.