If cables are laid in water pipes, the drinking water network must be opened more often than before for their installation and maintenance. This presents a risk to drinking water quality. Says UBA Vice President Thomas Holzmann, “Even if data cable systems are sterilized, the additional construction work to the drinking water network always entails the risk of dirt, microorganisms and pathogens entering drinking water. We therefore concur with the Commission’s opinion”. Furthermore, the presence of additional systems in water pipes increases surface area in the pipes and leads to sections where flow is reduced. In these sections, so-called biofilms can grow. These pose no problem when present in small amounts. When these biofilms become more pronounced, however, they are a preferred site not only for bacteria and other microorganisms but also for water lice and other small animals which find food there. While these creatures occur naturally in small numbers and then present no health risk, their presence in water pipes is obviously undesirable, particularly when it is frequent and in high concentrations.
As a general principle, drinking water distribution systems should be kept as simple and linear as possible. The EU Drinking Water Directive itself requires that no impurities associated with substances or materials used in the supply of water intended for human consumption shall remain in such water in concentrations higher than is necessary for the purpose of their use. The purpose of drinking water pipes is solely the transport of drinking water.
In any case, in the supply of drinking water the minimization rule in Articles 5 and 6 of the German Drinking Water Ordinance applies, mandating that the concentrations of microorganisms and substances that can contaminate drinking water must be kept as low as reasonably possible. This too militates against the drinking water network hosting other systems, according to the DWC at UBA.
UBA Vice President Thomas Holzmann says, “If local contamination occurs in water pipes and this is compounded by the presence of data cables, it is much more difficult to uncover its causes. The additional cable systems and connection points give rise to numerous new sources of dirt, pathogens and pollutants which then will all have to be checked.” The Federal Environment Agency therefore recommends that ducts should be installed in such a way that different media such as gas, water or data cables can flow or be transferred separately from each other in the first place. A suitable option for broadband deployment outside of water pipes are so-called empty conduits.
