4 inch Cast Iron Mushroom Vent Cap

4 Inch Cast Iron Mushroom Vent Cap – Roof Termination for DWV Systems

The 4 inch cast iron mushroom vent cap is engineered for use in gravity drainage systems requiring vent termination above roof level. Manufactured from Class 25 or better cast iron, this component serves as a protective closure on vertical vent stacks, ensuring proper system venting while shielding the line from weather and debris intrusion.

Material and Design Features

• ✔ Material: Gray cast iron conforming to ASTM A48, Class 25 minimum
• ✔ Finish: Asphaltic bituminous coating for corrosion resistance
• ✔ Construction: One-piece body with domed vent head for optimal discharge and water deflection
• ✔ Slot Openings: Evenly spaced for consistent airflow and pest prevention

Performance and Application

• ✔ Function: Terminates open-ended vent stacks in DWV systems, maintaining neutral air pressure and preventing trap siphonage
• ✔ Ingress Protection: Prevents entry of animals, foliage, and precipitation into vent piping
• ✔ Temperature Resistance: Suitable for outdoor exposure in all climate zones

Installation Guidelines

Intended for use on vertical vent stacks terminating through the roof, this vent cap is compatible with hub or no-hub cast iron piping systems. Use mechanical couplings or appropriate roof flashing detail as dictated by the roof assembly. Complies with installation clearances specified under the International Plumbing Code (IPC) and Uniform Plumbing Code (UPC).

Technical Specifications

• Size: 4 inch nominal pipe size
• Type: Mushroom style vent cap
• Connection: Slip-fit or hub mount depending on vent line termination
• Compliance: Satisfies air admittance and termination requirements per IPC/UPC

Common Use Cases

Used in multi-story residential, institutional, and commercial plumbing systems for terminating DWV vent stacks at the roof level. Also employed in retrofit projects where cast iron infrastructure is required due to fire, sound, or structural performance specifications.

Code Note

Per current plumbing codes, all vent terminations shall be protected from blockage and must extend above roof elevation by at least 6 inches (or more depending on jurisdiction). Vent caps must not reduce the vent pipe’s internal area.

Designed to meet the performance demands of high-traffic buildings and exposed environments, this 4 inch cast iron mushroom vent cap ensures reliable ventilation and long service life in DWV systems. A field-proven component for code-compliant installations.