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When the same type of leak keeps recurring, simply repairing the damage is not always enough. For Höganäs Municipality, the next step was therefore to investigate why the corrosion was occurring and whether it could be reduced. By taking a more preventive approach, the service life of existing pipelines can be extended while reducing the need for emergency repairs.
A water leak can be repaired. But when leaks keep recurring, it is worth asking: Why do they occur in the first place?
In Höganäs Municipality, as in many other Swedish municipalities, recurring leaks in the water and wastewater network are a problem that leads to both high repair costs and unplanned service disruptions. Repairing an individual failure solves the immediate problem, but not necessarily its underlying cause.
A closer investigation revealed that a well-known corrosion mechanism was part of the problem in Höganäs: differential aeration cells.
A buried metal pipe rarely remains in a completely uniform environment throughout its entire service life. Soil conditions can vary along the pipeline, for example at transitions between sand and clay. Previous repairs can also alter the conditions when new backfill material is placed around part of the pipe. These differences may seem minor, but from a corrosion perspective, they can have a significant impact.
When different parts of the pipe surface are exposed to different levels of oxygen, an electrochemical potential difference can develop. This creates what is known as a differential aeration cell, where parts of the metal surface become anodic and corrosion becomes concentrated in a limited area.
The result can be localized and accelerated corrosion – eventually leading to another leak. This also means that, in some cases, a previous repair can alter the environment around the pipeline in a way that creates new conditions for corrosion. The problem is therefore not only about the age of the pipe, but also about the environment surrounding it.
Once the problem areas had been identified, Höganäs Municipality chose to install the NoCor® corrosion prevention system. Rather than waiting for the next leak, the aim is to address the corrosion process itself and thereby prevent further deterioration of the pipeline. By stopping ongoing corrosion, the existing pipeline can remain in service and its technical service life can be extended. Under the right conditions, the solution can extend the pipeline’s service life by at least 20 years.
This represents a different way of approaching water and wastewater network maintenance. The question is no longer simply, “Where will we need to make the next repair?” but also: “Why is the damage occurring, and can we prevent it before the next leak happens?”
For Höganäs, this represents a step away from purely reactive maintenance towards exploring a more preventive approach. For a municipality, that difference can mean fewer emergency interventions, better opportunities to plan maintenance, and the potential to gain significantly more service life from pipelines that are already in the ground.
For example, a differential aeration cell can develop when the soil environment around part of a pipeline changes following a previous repair. Differences in oxygen availability can create an electrochemical potential difference, leading to localized, accelerated corrosion.
