At what length does a branch drain require a vent when it is being installed according to the New Zealand Building Code?

In accordance with the New Zealand Building Code, a branch drain generally requires a vent when it exceeds a length of 10.000 meters. This requirement is in place to ensure that proper airflow is maintained within the drainage system, which helps to prevent the creation of negative pressure that could lead to siphoning issues or the disruption of trap seals. Adequate venting is vital for the effective and efficient performance of a drainage system, as it allows gases to escape and prevents blockages.

Branch drains that extend beyond this specified length may not adequately function without a vent, as the longer distances can hinder the smooth flow of wastewater and potentially create odors or backflow problems. This is why the minimum length before a vent is required is critical for the design and installation of drainage systems in compliance with legislative standards.