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A review on the durability of PVC sewer pipes

Polyvinyl chloride (PVC) has become one of the dominant construction materials for sewer systems over the past decades, as a result of its reputed merits. However, since PVC sewer pipes have operated for decades in a hostile environment, concern over their longevity has been lately raised by sewer managers in the Netherlands. Towards that direction, the main factors and mechanisms that affect a PVC pipe’s lifetime are discussed in this article, along with the current lifetime prediction methods and their limitations. The review of relevant case studies indicates that material degradation, if any, occurs slowly. However, inspection (CCTV) data of three Dutch municipalities reveals that severe defects have already surfaced and degradation evolves at an unexpected fast rate. A main reason of this gap between literature and practice is the fact that comprehensive material testing of PVC sewer pipes is rarely found in the literature although it proves to be essential in order to trustfully assess the level of degradation and its origins.

Plastics are used for a wide range of commercial and industrial piping applications. The most known are polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), acrylonitrile–butadiene–styrene (ABS), polybutylene (PB) and glass–fibre-reinforced polyester (GRP or FRP). Concerning piping systems for drinking water supply, gas distribution and sewage disposal, PVC, PE and PP are the most popular polymer materials (PlasticsEurope, 2017). Especially for gravity sewer pipes, PVC has been extensively used over the past decades and has become the dominant construction material. Cost efficiency, ease of installation, range of available diameters (40–630 mm) and its reputed chemical resistance favour its wide acceptance by decision makers in urban drainage (Davidovski, 2016).

Since there are PVC sewer pipes in operation for at least four decades, concern over their longevity has been lately raised in the Netherlands. It is still unknown whether the expectations of long-lasting PVC pipes (Folkman, 2014) will prove realistic or new asset management strategies should be established in the near future. Knowledge of the current structural integrity of sewer systems is a key issue for establishing successful asset management strategies, leading to better decision making and more affordable investments. In practice, sewer managers currently base their strategies mainly on visual (CCTV) inspections (Van Riel, Langeveld, Herder, & Clemens, 2014). Subsequently, decisions are taken whether replacement, rehabilitation or a near future inspection should take place. However, linking the observed defects in CCTV to the actual physical state of a pipe is challenging (Van Riel, 2017). A necessary condition for achieving this is comprehensive understanding of the mechanisms that affect a PVC pipe’s lifetime, their combined effects and eventually their results, which are the defects found in practice. An overview of these mechanisms and their origins is included in this article. Lifetime prediction methods for UPVC pipes are also utilised to describe specific types of failure, while their ability to provide trustful lifetime prediction is discussed.