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Trenchless pipe rehabilitation for perfect drinking water pipes
The quality and the availability of water is essential for human health and the ecological system, and it is a basis for economic growth and development. Every year about 3.5 million people die as a result of poor water supply – and the world population is steadily growing. In addition to the challenges which water management faces in regard to the increasing demand for water, this year's United Nations international year of water cooperation has also pushed questions to the foreground concerning the accessibility and distribution of water, as well as water services.
Many million cubic metres of clean drinking water flow daily through the water pipes of the world. According to the statistic platform "Worldometers", the consumption increases by 64 billion cubic metres every year due to population growth. This is possible thanks to a technically refined, underground pipe network. Nonetheless, around the world, the increasing deterioration of the underground infrastructure is becoming noticeable. Pipe systems are ageing and the load capacities are increasing. The loss of drinking water caused by leaking water pipes as well as the contamination of groundwater due to leaking sewer, oil or industrial lines endangers man and environment. This is especially true for regions in which there is no drinking water treatment and the ground water is used unfiltered as drinking water.
Around the world, the supply network of many towns and municipalities suffers from material fatigue, lime scale deposits and corrosion. Pure drinking water leaks continuously into the surrounding ground soil of a defective water pipe, which can amount to up to 50 % of water, depending on the region and the age of the pipes. At 6.5 %, Germany has a relatively low leakage rate compared to other European countries, e.g. England 15.5 %, Poland 24.6 % (German Association of Energy and Water Industries, 2010). In Asian countries about 25 - 40 % of the valuable resource water is lost due to leaking water pipes (Asian Development Bank, 2010). During the United Nations World Water Year 2013, events are taking place around the world (like the Budapest Water Summit at October 8-11 and the International Water Week Amsterdam at November 4-8), to draw attention to this topic and to encourage dialogue. 
Advantages of the trenchless pipe rehabilitation of drinking water pipes
Measures to stop water loss and contamination generally cost just a fraction of water treatment or recovery. Trenchless pipe rehabilitation presents a time-saving and low-cost solution in comparison to new constructions. In contrast to renewal, no streets, pavements or built-up areas need to be dig up along the entire pipe length for rehabilitation to replace defective sections of the pipe with a new pipe. The rehabilitation is carried out directly in the host pipe whereby the manholes or small ditches serve as access points. This has proven to be a great advantage in inner cities with high building density and heavy traffic volume.
In the past 20 years, various trenchless rehabilitation processes were developed with which several hundred metres of drinking water pipes could be repaired as a unit from manhole to manhole. From an economical point of view, this means employing these technologies saves construction costs and time. According to a study of the GSTT (German Society of Trenchless Technology), about 70 % of the pipe renewal costs can be saved that otherwise would be spent during open-cut roadworks, earth removal, and subsequent reconstruction. A positive ecological aspect is the CO2 savings of about 70 %, as fewer construction machines are in operation, construction time is shorter, and there are fewer traffic jams due to road closures. In addition, nature remains undisturbed and the soil conditions as well as the roots of the trees are untouched. For the residents adjacent to the construction site, the trenchless rehabilitation means less disruption of normal life, as, compared to open-cut construction, only moderate disturbance occurs due to noise, dust and exhaust fumes. Depending on the technology and the severity of the pipe damage, water supply and disposal is also ensured during rehabilitation.
Requirements for the pipe liner procedure as drinking water pipe
Modern trenchless rehabilitation technologies such as Cured-in-Place (CIPP) quickly, economically and reliably provide for sealed line systems and ensure a maximal use of the water supply. Since water supply mains are operated as pressure pipes, there are two necessary requirements for liner systems: Firstly, the installed liner systems have to withstand the necessary inner pressures. Secondly, all materials that the liner is composed of must meet the high hygienic requirements as defined in the drinking water ordinances in order to be authorised for drinking water pipes.
Two reliable technologies in the field of trenchless rehabilitation are the NORDIPIPE™ and TUBETEX™ that fulfil different requirements based on their material structure and are already employed world-wide for the rehabilitation of drinking water pipes of 150 mm to 1200 mm diameter. The two CIPP systems differ in the liner materials used, as well as in the procedural details, such as installation or curing. Whereas TUBETEX™ is glued to the existing pipe and in effect becomes part of it, the NORDIPIPE™ is independent of the existing pipe. Thus the seamlessly woven polyester tube TUBETEX™ is usually installed as a precaution before the pipe breaks, whereas the statically self-supporting polyester needle felt tube NORDIPIPE™ is employed for rehabilitation when the existing pipe is already quite damaged or has deteriorated.
Trenchless rehabilitation of water mains in urban congested areas
In the metropolis of Hong Kong, NORDIPIPE™ liner was used to rehabilitate a 600-metre long, defective water pipe within two weeks without hindering the daily traffic. The liner was plugged into the host pipe with a diameter of 600 mm in three sections from one sewer manhole to the next. Steam curing was employed then to form it into a new pipe with static stability. 
In the old part of Montreal, Canada, the 100-year old drinking water pipe network was renewed with the pipelining product NORDIPIPETM, which neither hindered street traffic nor bothered retail business. Within two years, the roughly 4600 kilometres of defective drinking water pipes in the historic heart of Montreal were repaired and the survival of the underground network ensured.
TUBETEX™ liners were used in a residential neighbourhood in Barcelona to rehabilitate 600 metres of a water pipe. The construction project was divided into six sections and was completed within just three weeks. The heavily soiled existing pipe was prepared for the liner installation first of all by cleaning with high-pressure. After the inversion of the TUBETEX™ liner, it was hardened into a new pipe that, even though it is fused to the host pipe, is elastic enough to compensate movements and knocks against the line from soil loads.
Perfect drinking water pipes for the next decades
With the growing world population and the concurring increase in water consumption, water mains must be in fault-free condition to ensure the supply with clean drinking water without loss of the valuable commodity. In regions in which a regulated water supply is accessible, trenchless pipe rehabilitation technologies have a high potential for solving pipe problems. Apart from the lower costs, they contribute significantly to transporting clean drinking water to the end consumer, avoid water pollution and actively protect the climate by reducing CO2 during the rehabilitation process.