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Systems - Rain Plus

Rainplus Siphonic Rain Water Collection System

Rainplus® is a siphonic rainwater drainage system that uses the building height as the driving force to generate high speed flow rates thus maximizing drainage efficiency with the lowest levels of water accumulation on the roof. Valsir technology fully meets the increasing levels of rainfall and guarantees the drainage of medium to large size buildings in total safety.

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This technology offers numerous advantages;

  • Significant cost savings. When compared to conventional systems, Rainplus® requires a lesser number of roof outlets, down pipes and associated ground terminals, a substantial reduction in pipe diameters and the number of fittings required. This results in savings of up to 80% on vertical pipes and from 20% to 30% across the entire system.
  • Space savings. The fewer number of roof outlets are connected to single horizontal collector pipes that are fitted without fall thus increasing space within the building.
  • Building and site design flexibility. The fewer number of downpipes are positioned anywhere along the building perimeter thus allowing greater freedom with building aesthetics.
  • Eco sustainability. The ease in directing the pipes to storage tanks makes the collection of rainwater easier for recycling. The system itself uses environmentally friendly and recyclable HDPE.
  • High performance. When in operation the drainage pipes flow at 100% full over the entire system, draining velocity is therefore greater resulting in a self-cleansing action.

Rainplus vs. Conventional Systems

Conventional Gravity System

There are two types of rainwater drainage systems: conventional systems that are incorrectly called gravity systems, and the Rainplus® siphonic system, which is also known as a vacuum system or full section system. Both use the force of gravity but in a decidedly different manner, resulting in differences in performance, design and calculation.

A conventional drainage system allows considerable amounts of air into the pipes - up to 80% of the pipe section. The outlets are simple “funnels” installed on the roof covering and connected to the downpipes which are as high as the building and the water collectors which require a gradient of at least 1%, are dimensioned for a maximum filling factor of 70%. When the water collectors are very long and it is not possible to provide the minimum slope necessary due to the limited space available, the only solution is to increase the size of the pipes with a consequent rise in installation costs.

Rainplus® Siphonic System

Standard downpipe layout

Rainplus® Downpipe layout

Rainplus® is defined as a siphonic rainwater drainage system because it is based on the same principle as a siphon. The siphon principal is commonly used to transfer fluid from one container to another located in a lower position. When the pipe is full, the fluid tends to fall towards the lower outlet due to its weight causing the suction of the liquid from above. This process only starts when the pipe is completely full and the driving force that causes this effect is a result of the difference in height of the two containers: the bigger the difference, the stronger the driving force and, as a consequence, the greater the flow velocity in the pipe.

The performance of the Rainplus® siphonic drainage system is therefore decidedly better than a conventional system where the driving force is generated exclusively by the amount of water that accumulates on the roof. When the siphonic drainage system runs at full capacity, the “syphon effect” is triggered resulting in a driving force that is proportionate to the height of the roof and the end of the circuit, which is typically located at ground level. Such power generates levels of positive and negative pressures in specific points of the circuit which rapidly increase the velocity and flow rates of the system.

Engineered System Design

Unlike conventional gravity systems, a high degree of engineering and expertise is necessary, both in the design and installation phase. 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 analysed.

Bernoulli’s principle

In fluid dynamics, Bernoulli’s principle states that for an inviscid flow, an increase in the speed of the fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid’s potential energy. Bernoulli’s principle is named after the Dutch-Swiss mathematician Daniel Bernoulli who published his principle in his book Hydrodynamica in 1738.

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 to above the anti-vortex plate, 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.

System Components

Rainplus® Roof Outlets

  1. Wide range of drainage flows (up to 65 l/s with Rainplus® 40-110 and up to 14 l/s with Rainplus® 56).
  2. Reduced roof water levels required to trigger the syphonic action.
  3. No swirling thanks to the special profile of the anti-vortex blade and reduced pressure losses at the inlet.
  4. Low noise levels.
  5. Maximum operation stability.
  6. Easy installation thanks to the reduced number of components and compact size. For example, Rainplus® 56, in the version with horizontal connection, can be installed inside the roof slab thanks to a height of just 104 mm.
  7. Connection with the Valsir PE® system is extremely reliable.
  8. Suitable for installation in gutters, even of small dimensions, or on roofs covered with any type of waterproofing material.
  9. Anti-leaf grating has a special profile that does not compromise outlet performance.

HDPE Pipe and fittings

Valsir 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.).

Valsir HDPE® is the ideal solution for the construction of siphonic drainage circuits thanks to its numerous advantages:

  1. Available in a wide range of fittings in diameters 40mm up to 315mm.
  2. Butt welding and electro-fusion jointing options.
  3. Possibility of pre-fabricating system parts and mounting them on site thanks to its light weight.
  4. Savings in labour costs thanks to rapid installation times.
  5. No material wastage makes it more economical.
  6. Increased safety of the systems thanks to the excellent mechanical characteristics.

Design Service and Support

Rainplus® Roof Outlets

Waterware and Valsir’s technical team collaborate on the system design using advanced Rainplus® software. Waterware’s tech team have been trained in Italy to generate the initial design which gets exported for overnight approval by Valsir’s engineers.

Unexpected obstacles or changes to the building during construction phase are not uncommon. As a result, any modifications required to the initial design are processed immediately in house so that no delays impact construction deadlines.

Rainplus® software parameters

The software uses the following parameters to generate a design;

  1. Rainfall intensity.
  2. AutoCAD® drawings, both floor and elevation plans.
  3. Surfaces to be drained and preferential positions for outlets.
  4. Construction characteristics of covering and indication of any gradient.
  5. Drawing and characteristics of gutter or drainage channel in the case of parking areas.
  6. Municipal storm water main and indication of connection points.
  7. Preferential position for downpipes.

Installers with existing experienced in HDPE can be quickly up-skilled to perform Rainplus installations with guidance from the Waterware tech team. HDPE system training and site visits are provided as required depending on the relative experience of each installer.

Quality Assured

Achieving maximum reliability is of critical importance to Valsir and a quality control system in compliance with the UNI EN ISO 9001:2008 standard has been introduced to manage all of the production units and processes.

Valsir currently holds over 150 product approvals from around the world demonstrating its ability to produce a wide range of products to a very high standard.

In addition Valsir carries out numerous in-house tests that are not specifically required by the standards but are regarded as essential to ensure the absolute best product quality and excellence. Internal inspections of the manufacturing processes, raw material tests, laboratory analyses, stress tests, installation simulations and technical research and development all contribute.

Project References

The combined experience gained over the years by the technical staff of Valsir and Waterware represents a reliable support base for designers and installers.

The larger number of installations carried out around the world are a tangible demonstration of an advanced and reliable product.

Eden Park Auckland NZ

Claudelands Hamilton NZ

General Electric Oil & Gas Perth Austalia

Teatro Daiz e Velarde Madrid Spain

Blue Route Mall Capetown South Africa

The Villa Mall Pretoria South Africa