Until the early 1980’s the most commonly used rainwater management solution within the industry was the gravity drainage principle, this is where water flows naturally into a series of pipes penetrating the building fabric through inlets and running vertically from roof level to ground at multiple locations within the building.

The bigger the building, the greater the number of penetrations and intrusive rainwater pipes, which impacts on usable floor area as each pipe needs to be adequately protected from possible damage during the useful life of the building. With each new penetration and rainwater pipe there is a greater risk of water ingress into the building.

The effectiveness of the gravity-fed rainwater system was called into question when buildings started to increase in size. The gravity-fed principle suffers from limited efficiency when used on a larger building as the requirements for the number of downpipes need to successfully manage the rainwater volumes becomes unviable. This led to the introduction of siphonic rainwater management systems in mid 1980s.

Traditional Siphonic systems allow water to be drained from the roof at up to four times the speed of conventional gravity drainage, with the same amount of inlet penetrations, but radically reducing the number of downpipes. This increases the usable floor area within the building.

However, as a consequence, an increase in internal pipework is introduced at high level; for every linear metre of gutter, there are more than two metres of main collection pipe and tail pipes required to operate a siphonic rainwater system correctly. The existence of such significant amounts of siphonic pipework transporting large volumes into the building still leaves potential for catastrophic water damage in the event of a failure of any one of the multitude of joints and connections within the building.

Additionally, the pipework and support and restraint bracket installation for this kind of system must be undertaken by specially qualified operatives working at height from access equipment. It also requires that other construction operatives cease work and clear the installation area to avoid the risk of falling objects. All of which adds time and cost to the completed project, but these problems have been generally regarded as a ‘necessary evil’ in order to improve the rainwater management system.

In 2007 CA launched the Caskade^® HYDRA evolved siphonic rainwater management system. After extensive research and development Caskade^® HYDRA offers a solution to the rainwater management risks.

In stark contrast with gravity-fed and traditional siphonic systems, Caskade^® HYDRA utilises two integral rainwater collection chambers – a first stage, which drains to a single downpipe at one end of the building, and a second stage which drains to a single downpipe at the opposite end. The rainwater flows through individually calibrated Anti-Vortex inlets into the chambers to a downpipe, which are designed to cater for the rainwater design flow capacity of the roof. When the first stage channel reaches capacity the secondary channel is brought into action, discharging the remainder of the designed storm flow, to further protect the building. Keeping rainwater discharge where it belongs – completely outside of the building envelope.

Ingress of water can be devastating to a business and is often very costly. Building owners, designers and specifiers spend damaging amounts of time and money to ensure that roofing and cladding systems are weathertight and not susceptible to water ingress. Yet when designing or specifying a rainwater management system it is deemed acceptable to deliberately introduce rainwater and all the associated risks into a building.

The Caskade^® HYDRA rainwater management system eliminates water ingress by managing the rainwater requirements completely outside of the building. The body of the Caskade^® HYDRA gutter system contains two sealed siphonic water chambers. A first and second stage, The rainwater flows through calibrated anti-vortex inlets into the first stage chamber to an individual downpipe, which is designed to cater for the initial rainwater capacity of the roof. Should the first stage channel reach capacity, such as in extreme storm conditions, the second stage channel is brought into play, discharging the remainder of the designed storm flow, to further protect the building. Keeping rainwater discharge where it belongs – completely outside of the building envelope.

In recent years, the boundaries of architecture have been stretched to the limit, with building lengths greater than 200 metres becoming commonplace. This development will only intensify the potential risks associated with vulnerable and intrusive high-level internal pipework caused by the installation of a conventional siphonic rainwater management system.

An increase in building length leads to an increase in rainwater volumes and the amount of pipework needed to cope with such volumes. Pipework that is not only expensive, but unsightly and takes up valuable space needed by the building's tenant and also introducing an unnecessary risk of failure into the building.

The Caskade^® HYDRA system delivers exceptional rainwater management, whilst removing the issues and costs associated with intrusive pipework –as it eliminates the need for internal pipework in all but the very largest of buildings.

If a standard siphonic system is incorporated into a buildings design it’s not just the rainwater ingress risks that can cause problems for building owners and project manager’s. Keeping to the projects critical build path is of the up most importance if unnecessary costs are to be avoided. When installing typical siphonic systems the project critical path can be some cause for concern. The internal pipework installation programme will need to be taken into account and the time and resources needed to install the internal pipework will need to be factored into the over all project schedule.

The Caskade^® HYDRA evolved siphonic rainwater management system offers real project schedule and cost benefits as it does not require the internal installation programme, risk assessment and management needed for internal pipework, removing man-hours, working at heights, falling object risk and clear working area requirements, reducing the overall project schedule.

The system is fully calibrated for total inflow control and capable of handling the most extreme rainfall intensities with ease. Tested to extreme worst-case conditions at the University of Sheffield, verified for negative pressure resistance by UKAS and with full capacity calculation service using advanced rainwater analytical software techniques, each Caskade^® HYDRA installation is tailored for the specific project, providing a unique rainwater management solution every time.

There are no delays in the primary compartment going negative as the Anti-Vortex plate flows directly in and does not require any tail pipes.

During the installation of conventional siphonic systems the siphonic outlets will be sealed to avoid water ingress into the building. Instead temporary drainage measures will be put into place while the system is being installed.

The Caskade^® HYDRA evolved siphonic rainwater management system is fully operational once the gutter has been installed, eliminating the need for temporary drainage management and moreover, there is no surface water to create slip hazards to operatives.

Traditional siphonic systems struggle with contraction and expansion issues as rainwater is always taken from the cold exterior of the building to the warm interior through internal pipes. Due to contraction and expansion considerations, these pipes need to be bracketed and restrained to avoid movement and vibration.

With Caskade^® HYDRA, this problem is eradicated as the system removes the need for internal pipework within the building. All rainwater is managed completely outside of the building, meaning the temperature of water remains the same and no contraction or expansion issues will occur. This not only eliminates the problem but helps to reduce project costs, as there is no need to install costly pipework or put measures into place to reduce vibration and noise contribution associated with contraction and expansion.