Rainplus®, the ultimate solution in case of rain
Rainplus® represents the most modern technology in the constructions sector and in the drainage of rainfall from the roofs of medium and large size buildings. The system makes use of the building height as the driving force, which together with the effect of negative pressure, allows high speed flow rates to be reached thus maximising drainage efficiency.
Rainplus® allows the entire flow of water to be directed to any part of the building whatsoever, thus enabling the most modern rainwater harvesting systems to be installed as required by the Green Buildings Program.
The Rainplus® siphonic drainage system is made up of special outlets that are patented, designed and tested to American Standard ASME A112.6.9 and European Standard EN 1253 and connected to HDPE® high density polyethylene pipes. The outlets also incorporate special components that allow installation on any type of roof and waterproofing sheet.

The documentation

Characteristics of excellence

Flow stages

EN 1253 and ASME A112.6.9 technical standards are used to evaluate the performance of a siphonic system and, as they define the measurement method of the flow rates as a function of the water depth on the roof, they allow the flow regime phases to be analyzed.
Stage 1
With a moderate flow, of 10 or 15% of the design rainfall intensity value, the roof outlet works as it would in a conventional system and the flow is defined “gravity flow”, in that air content in the pipes is elevated.
Stage 2
When the water discharged from the roof is between 10 to 15% and 60% of the full bore flow condition, water flow is discontinuous and the system therefore fluctuates from a gravitational flow regime to a full siphonic action. At these rainfall values the water that accumulates on the roof fills the outlet, cutting off air flow into the pipe and triggering the siphonic action.
The velocity of water discharged therefore increases which results in falling water levels, allowing air to be drawn into the piping network and breaking the siphon; for this reason this stage is called “plug flow”.
Stage 3
When the water discharged is between 60% and 95% of the design rainfall intensity value, the pipes are completely full of water although many air bubbles are still present. This stage is called “bubble flow” and features high flow velocities thanks to the siphonic effect.
Stage 4
When the flow is over 95% of the design rainfall intensity value, the siphonic effect operates at full capacity reaching maximum velocity with no air entering the pipes. This stage is called “full flow” and does not produce noise or vibrations.

A quality made system

The Rainplus® siphonic system is made up of roof outlets, pipe clamps and other clamping accessories, Aperto HDPE pipes and fittings, a software for 3D design and extremely professional computations. Aperto HDPE pipes and fittings are manufactured to EN 1519 and have been approved to many standards worldwide (CSTB, IIP, KIWA, SKZ, ETA, Lloyd’s Register, etc.). The light weight and wide range of pieces available make Aperto HDPE the ideal solution for the construction of siphonic drainage circuits. Aperto HDPE also offers great installation flexibility thanks to the various jointing methods, such as butt-welding and electrofusion.
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Case history

Rainplus is an innovative system that was installed all over the world.


Sydney (Australia)


Novo Mesto (Slovenia)

Blue Route Mall

Capetown (South Africa)

General Electric Oil & Gas

Perth (Australia)