PAM-Global EPAMS Syphonic Roof

Drainage System

Traditionally, the rainwater is collected from the roof at regular points by gravity flow. The larger the roof area is, the more numerous the points are.

In the alternative method, called « syphonic », the run-off water is drained in pipeworksoperating at full bore, harnessing the principle of mechanical energy conservation between the high spots, rainwater outlets, and the low spot which is the main drain



In case of intense rainfall, the rainwater flows towards the outlet equipped with an anti-vortex mechanism. When the grid is half covered by rainwater -30mm- the mechanism limits the entering of air into the pipe system and initiates negative pressure.As the speed and the water flow still increases, the air entering the system decreases; it creates suction of the water into the roof outlets. When no air is entering the pipework, the drainage capacity of the siphonic system is at its optimum level.



Once the system is fully primed, there is an abrupt increase of velocity within the pipes and they flow full bore under negative pressure. Because the system flows under pressure, the majority of the pipework can be horizontal rather than vertical. So, compared to gravity systems, siphonic velocity allows:

  • smaller pipe sections
  • long horizontal runs without gradient whichcan be installed very close to the roof or ceilingand reduced need for vertical pipework.

Rooftop Drainage in Total Safety

In case of intense rainfall, safety rests with quick and efficient drainage. The safety of EPAMS® siphonic systems leans on three cornerstones:

  • Accuracy of the design study and project follow-up, including coordination and installation in full compliance with the study.
  • Products design: suitable siphonic outlets plus pipes and brackets able to withstand negative pressure and dynamic loading from siphonic flow.
  • Clear guidance for maintenance requirements.

Design Accuracy

A siphonic roof drainage system is truly an≪ engineered system ≫ which must be designed withcareful and expert analysis. The pipework design is the key factor for performance and operational safety. SAINT-GOBAIN PAM salesmen, trained to the EPAMS® system, first evaluate your roof drainage project. When feasibility is confirmed, a technical team, designs both technical study and network sizing using the dedicated EPAMS® Software.

This thorough management of the EPAMS® projects - feasibility study, project follow-up and control after installation completion – is carried out to ensure the EPAMS® system efficiency and provides the project manager with total peace of mind.

Product Design

Siphonic systems are sometimes considered to involve potential risks of claims and losses. Specific care has been brought to the design of the EPAMS® outlets to enhance their absorbing capacity up to 8l/min/m2 * which corresponds to a rainfall amount of 480 mm/h.

The extended surface of an EPAMS® outlet represent 700 cm2 which can be compared to a DN300 gravity flow outlet and then means no more risk!

EPAMS® outlets are 100% metal to provide mechanical strength and durability. There is no risk of damage during insulation and waterproofing works on rooftops.

They fully comply with EN 1253 for flow capacity, water tightness, solidity, mechanical strength, resistance to heat and climatic stresses (resistance to Ultra Violet…).

EPAMS® grid and the anti-vortex device are made in one piece which allows quick removal with no risk of error at reassembling and ensures easy intervention and maintenance.

EPAMS® being an all metal system is stable and serviceable in total safety, over a long period of time.

Please contact with us for more information!