A relief vent is required when there are how many or more branch intervals?

A relief vent is required when there are 10 or more branch intervals present in a plumbing system. This requirement helps prevent the potential negative effects of pressure that can build up within the drainage system, which could impede proper flow or lead to issues like sewer gas venting improperly. The relief vent acts as a means to relieve this pressure, ensuring that wastewater can flow freely and reducing the risk of blockages or backups.

When there are fewer than 10 branch intervals, the system can typically manage with the existing venting requirements without necessitating a relief vent. This rule is part of plumbing codes intended to optimize system functionality and maintain safety standards.