What diameter must a section of drain acting as a vent be at a minimum?

For a section of drain that is acting as a vent, the minimum diameter is crucial for ensuring proper ventilation and effective drainage system performance. A vent allows air to enter the drainage system, which prevents vacuum formation that could impede water flow, and it also helps in the efficient escape of sewer gases.

The selection of a 65 mm diameter for a vent complies with standard plumbing practices that dictate the appropriate size for various types of venting scenarios in drainage systems. Vent sizes that are too small may lead to restrictions in airflow, causing drainage issues, while larger diameters are typically not cost-effective and may exceed necessary requirements.

Choosing 50 mm or 80 mm for this function does not meet the established guidelines for vent size which emphasize that 65 mm is the minimum acceptable diameter for a venting section. A 100 mm vent would exceed the minimum requirement but is not needed for most standard applications, which again points towards 65 mm as a practical and effective size for maintaining ventilation in a drainage system.