Effective roof drainage protects structures from costly water damage, membrane stress, and safety hazards. The Zurn Z125 8-3/8" Diameter Roof Drain with Low Silhouette Dome is engineered for consistent stormwater performance on flat and low-slope commercial roofs. Its compact diameter, watertight membrane interface, and low-profile dome combine to deliver high intake capacity while resisting wind uplift and debris buildup.

Zurn Z125 Roof Drain Diagram

What Is the Zurn Z125?

The Z125 is a primary roof drain featuring an 8-3/8" diameter bowl paired with a low silhouette dome. The low-profile dome maximizes intake area while staying unobtrusive to rooftop traffic and resisting wind effects. Designed for long service life, the Z125 integrates with common commercial roof membranes via a secure flashing clamp for a watertight seal.

Key Features & Benefits

• Low Silhouette Dome: High intake with reduced wind uplift and less debris snagging.
• Compact Footprint: 8-3/8" diameter supports strong hydraulics without crowding rooftop layouts.
• Watertight Membrane Interface: Flashing clamp helps prevent infiltration at the drain transition.
• Durable Construction: Built for harsh rooftop exposure and heavy storm events.
• Service-Friendly: Dome access supports routine inspection and cleaning.

Zurn Brand Quality

Where the Z125 Excels

• Commercial and industrial flat or low-slope roofs
• Institutional buildings (universities, hospitals, government)
• Warehouses and logistics centers with large catchment areas
• Retrofits replacing undersized or aging roof drains

Installation Considerations

Proper installation is crucial for long-term performance and code compliance. Use these best practices:

• Set the drain at roof low points to promote natural runoff toward the bowl.
• Clamp the membrane securely to achieve a watertight seal; verify per manufacturer torque guidance.
• Ensure the dome is accessible for inspection and cleaning—especially after major storms.
• Confirm outlet size and connection type match the leader piping and hydraulic calculations.
• Water-test the assembly during commissioning to verify flow and check for leaks.

Zurn Z125 Roof Drain Schematic

Case Study: University Science Building

Challenge: A midwestern university experienced ponding around rooftop mechanical zones during heavy rain, driving emergency service calls and increasing membrane wear.

Solution: The facilities team replaced legacy drains with the Zurn Z125 at critical low points. The low silhouette dome improved intake around mechanical curbs without catching debris, and the flashing clamp ensured a tight membrane interface.

Outcome: Ponding was eliminated across the affected zones. After two storm seasons, maintenance requests dropped significantly and membrane inspections showed reduced stress at prior problem areas.

Conclusion

The Zurn Z125 8-3/8" Diameter Roof Drain with Low Silhouette Dome offers dependable stormwater control for commercial and institutional roofs. Its compact bowl, efficient dome, and watertight membrane connection make it a reliable, service-friendly choice for new construction and retrofits alike.