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Kaytech drainage for excessive groundwater at The Willows

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A private home in a housing development threatened by a massive amount of groundwater has recently been saved by an innovative and highly economical Kaytech drainage system.

The site, at The Willows in Lynnwood, Pretoria, was constructed on a very steep gradient created by a cutting in one of the Magaliesberg Mountains. Since the resulting groundwater was posing a serious hazard to the foundations and walls of the home under construction, the on-site engineer proposed using Kaytech’s FloDrain, bidim and Kaypipe geopipe to provide effective subsoil drainage.

The solution involved applying a torch-on waterproofing system to the subterranean walls followed by a protection layer of polystyrene panels. The FloDrain fin component was then installed vertically against the outside of the wall and connected to a conventional bidim A2 filter geotextile wrapped drain comprising a M100 Kaypipe geopipe collector encased in stone aggregate. Impro, contracted to install the Kaytech subsoil drainage system, commenced the project in November 2016.

FloDrain is an easily installed prefabricated geocomposite drainage system supplied in lightweight, flexible 30 metre rolls pre-wrapped in a geotextile filter jacket of Kaytech’s renowned bidim. The system intercepts groundwater seepage and effectively lowers the water table in a wide variety of applications, such as subsoil drainage for roadsides, sportsfields and retaining walls. FloDrain is an economical and practical method that significantly reduces the costs of transportation, labour and materials.

Supplied in various grades, bidim is a continuous filament, nonwoven, needlepunched geotextile manufactured from 100% recycled polyester. The needlepunching process imparts several advantages including appreciable thickness, high porosity and a high throughflow capacity both normal and transverse to the plane to fulfil the drainage function. Bidim also performs other functions when incorporated in subsoil drainage, namely that of filtration and separation. Fine soil particles migrating under hydrostatic pressure are prevented from entering the drain while water passes through, thus lowering the phreatic surface in the surrounding soil.

To cope with the excessive amount of groundwater seepage at different levels across the cut face, the contractor installed the FloDrain system at varying heights.

Specially designed Kaypipe geopipe is the most practical solution for all drainage problems. The 70% perforated surface area of Kaypipe geopipe provides the highest infiltration rate compared to any other drainage pipe, thereby allowing for smaller diameter Kaypipe geopipes to be used. Manufactured from HDPE, Kaypipe geopipe is lightweight and flexible and much easier to handle than other drainage pipes. Although Kaypipe geopipe can tolerate extremely high stresses and does not become brittle even in low temperatures, it was proposed that a conventional drain be installed at the base of the FloDrain, as the Kaypipe geopipe could possibly be crushed by the sheer amount of compacted fill to be placed above it.

By completion of the project, 210 metres each of FloDrain and Kaypipe geopipe had been installed as well as 207 m2 of bidim A2. When heavy rains were experienced soon afterwards, with no detection of water or dampness in either the foundations or walls of the house, the project was deemed a great success.

For more information on Kaytech products and systems, visit

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