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Thorne Rainwater Systems are one of the UK leaders in Siphonic Roof Drainage Systems.

Our highly motivated team are fast to react to new building demands.

Our company has invaluable skills to cope with any project challenges.



In principle, siphonic drainage is a very simple process. Unlike traditional roof drainage, which is designed to flow part full, a siphonic system operates at full capacity, when water is sucked or siphoned from the roof down into the drain at high velocity.


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. The risk of overloading can be an issue with large areas of drain run-off water from building roofs.



Geberit HDPE discharge pipes are suitable for a multitude of application ranges in building drainage, roof drainage, in industry, in commercial or laboratory facilities, for placement in the ground, in concrete or in bridge construction.

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When you discharge waste water from domestic, civic and commercial buildings, you need robust, reliable and sustainable systems. Plastic pipe systems are proven solutions for soil and waste discharge.

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Drain Roof is a range of rainwater outlets and accessories. The roof drains which can be used for all types of flat roofs with bitumen or single ply roof membrane, are suitable for gravity and siphonic applications.

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Why use siphonics

Siphonic rainwater systems has many advantages over convention roof drainage solutions. Whether you are considering a new build or upgrading existing premises a compact, space efficient system, answers many questions. Demands from architects, civil engineers, surveyors, consultants and contractors on modern buildings can often make the installation of conventional rainwater drainage a difficult task.

Rainfall Intensity

Several factors have to be considered to make siphonic rainwater system work effectively. Specially designed roof outlets take into account rainfall intensity rate and to design the pipework configuration to optimise performance.


Rainwater Collection

Rainwater can be easily routed to collection tanks for future recycling, e.g. rainwater harvesting, irrigation, fire ponds, etc.

You can talk to us direct or arrange your architect or contractor to organise the first phase meeting to discuss future project requirements.

Multiple Applications

The drainage system is suitable for a multitude of applications in industry or laboratories. The polyethylene used is resistant against most standard alkalis, acids and chemicals, as well as hot water up to 80 °C.

UV Protection

The polyethylene used contains special additives which effectively protect against UV rays. The weatherproof pipes can therefore be stored outdoors for months. The pipes and fittings withstand shocks, drops, impacts or short-term pressure without breakage or permanent deformation.

Efficient Solution

Land can be expensive. therefore a more compact system, with simple and rapid installation, is an advantage. The hydraulically optimised geometry of the fittings ensures a high discharge capacity in the drainage system and allows both an economical dimensioning of the pipes as well as a space-saving configuration of the pipe ducts.