HDPE technical guides · 04
Geberit Pluvia
Design syphonic rainwater drainage for large roofs.
Geberit Pluvia is a syphonic roof drainage system. Roof outlets, Geberit HDPE pipework, supports and hydraulic calculations work together. It is particularly relevant to large roofs where downpipe locations and the space below the roof influence the design.
Understand the hydraulic principle
At the design flow, the system is intended to operate with water-filled pipes. The outlet's functional element limits air entry and the available height difference contributes to syphonic flow. Performance depends on the complete network geometry. Adding a Pluvia outlet to arbitrary pipework does not create a properly sized system.
Match the outlet to the roof build-up
Specify whether the roof includes a synthetic membrane, bituminous waterproofing, insulation, gutters or a green roof. Waterproofing connections and accessories must match this construction. Coordinate selection with the waterproofing contractor and designer so the interfaces are resolved before openings and structural provisions are made.
Provide the required calculation inputs
The design requires contributing roof areas, design rainfall, roof levels, the proposed route, drop heights and the downstream connection point. Calculations determine diameters and check each section's operation. Significant changes in length, level or fittings should be reviewed before installation because they may change the hydraulic balance.
Plan emergency drainage and maintenance
Distinguish the roof's primary drainage from its planned emergency drainage. Provide access to outlets, debris removal and inspection after exceptional events. The Pluvia support system forms part of the suspended pipework design. Selection of rails, anchors and hangers must be coordinated with the building's supporting structure.
What a Pluvia design file should contain
| Element | Information to validate |
|---|---|
| Roof | Areas, levels, waterproofing build-up and low points. |
| Design rainfall | Intensity and assumptions selected by the designer. |
| Outlets | Type, location, connection and access. |
| HDPE network | Route, diameters, heights and downstream connection. |
| Supports | Rails, anchors, hangers and structure. |
| Emergency drainage | Separate planned flow path and discharge point. |
Sizing requires the methods and tools intended for Pluvia. Reductions in pipe sizes or downpipe numbers are project-dependent, not a universal ratio.
Prepare for your project
- Roof plan with areas and elevations.
- Waterproofing and insulation details.
- Project rainfall assumptions.
- Under-roof route and downpipe locations.
- Outfall, emergency drainage and maintenance access.
Frequently asked questions
Can any collector be installed without a fall?
No. A no-fall arrangement applies to the sections designed and calculated within the Pluvia system. It does not automatically apply to conventional gravity drainage.
Can a downpipe be altered after design?
Changes to routes, diameters or levels can affect hydraulic operation. Have calculations and drawings revised before altering the network.
Does a green roof need specific accessories?
Yes. Outlets and accessories must suit the roof build-up and documented application. Drainage pathways and maintenance access must remain part of the design.
HDPE documentation
Geberit PE and tools catalogue · PDF HDPE documentationGeberit technical references
Continue planning
Discuss your project with EDIFIS
Send the drawings and network constraints so we can identify components to review, useful documents and availability to confirm.