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Plumber Red Seal · Question

A plumber is installing drainage for a dishwasher in a residential kitchen. The dishwasher P-trap is located 1.8 m from the vent stack. What is the maximum allowable developed length for the unvented branch of the dishwasher drain to meet NPC requirements?

According to NPC Table 2.5.7.1.(1), the maximum developed length of a pipe branch between a trap weir and its vent for a 40 mm pipe connected to a single fixtur

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Question: A plumber is installing drainage for a dishwasher in a residential kitchen. The dishwasher P-trap is located 1.8 m from the vent stack. What is the maximum allowable developed length for the unvented branch of the dishwasher drain to meet NPC requirements?

Answer options:

  • 2.5 m
  • 3.0 m ✅ 3.5 m
  • 4.0 m

Correct answer: 3.5 m

Explanation: According to NPC Table 2.5.7.1.(1), the maximum developed length of a pipe branch between a trap weir and its vent for a 40 mm pipe connected to a single fixture with a maximum 3 fixture units (a dishwasher typically has 2 DFUs) is 3.5 m. The distance given is less than this. Other options are incorrect as they do not align with the standard developed length limits.

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