Plumber Red Seal · Question
A plumber is installing a new kitchen sink in an existing residential dwelling. The sink drain is connected to an existing 38 mm (1 1/2 inch) trap arm that is 1.8 metres long. According to NPC guidelines, what is the maximum permissible developed length for a 38 mm trap arm from a fixture to its vent stack?
According to NPC Table 7.5.6.3., the maximum developed length for a 38 mm (1 1/2 inch) trap arm is 1.5 metres. The existing trap arm of 1.8 metres exceeds this
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Question: A plumber is installing a new kitchen sink in an existing residential dwelling. The sink drain is connected to an existing 38 mm (1 1/2 inch) trap arm that is 1.8 metres long. According to NPC guidelines, what is the maximum permissible developed length for a 38 mm trap arm from a fixture to its vent stack?
Answer options:
- 1.0 metre ✅ 1.5 metres
- 2.0 metres
- 2.5 metres
Correct answer: 1.5 metres
Explanation: According to NPC Table 7.5.6.3., the maximum developed length for a 38 mm (1 1/2 inch) trap arm is 1.5 metres. The existing trap arm of 1.8 metres exceeds this limit. Installing anything longer than 1.5 metres for a 38 mm trap arm is a code violation.
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