What size vent is required for a roof storm drain?

In plumbing design, the requirements for venting can vary based on local codes and the specific application of the drainage system. For roof storm drains, it is often determined that no vent is needed due to the nature of the system and how stormwater is handled.

A roof storm drain typically operates as part of a gravity drainage system that directs rainwater away from the roof and into the building's drainage system. Since stormwater systems primarily account for large volumes of water in a short duration, the flow does not create the same venting requirements that are seen in wastewater systems, where venting is necessary to allow air into the system to prevent siphoning and pressure issues.

Because of this specific function of roof storm drains, they are designed to handle the rapid influx of water without the need for additional vents, allowing for efficient drainage during heavy rainfalls. This understanding reinforces the conclusion that no vent is needed for a roof storm drain system.