Corrosion protection of district heating systems

5 February 2026

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Challenge

Oxygen in district heating water is one of the primary causes of corrosion in piping systems and a major factor in reduced system lifetime and increased operating costs. During repairs, system expansions and component replacements, oxygen is inevitably introduced into the network, increasing the risk of corrosion and damage.

Transmission company VEKS, which supplies heat to 20 local district heating utilities in the Copenhagen area, sought a future-proof and environmentally responsible solution to protect its district heating infrastructure and maintain consistently high water quality — without relying on chemicals.

Solution

In 2013, VEKS commissioned a large-scale catalytic de-oxidation (DeOx) system from BWT — the first installation of its kind at this scale. The DeOx technology removes oxygen from district heating water through a catalytic process, operating entirely without chemicals and with minimal environmental impact.

The DeOx plants are installed directly into the district heating loop and automatically remove oxygen whenever needed. The solution is dimensioned according to system requirements and ensures stable, high water quality even during periods of increased oxygen ingress caused by maintenance or network expansion.

Inspired by the success at VEKS, the technology has also been implemented internationally. At Stanford University, where a traditional steam system was replaced by a modern district heating system, BWT’s DeOx technology was selected to support the university’s ambition for long-lasting, chemical-free and sustainable infrastructure.

Result

Today, three BWT DeOx systems with a capacity of 150 m³/h each operate in the Copenhagen district heating network, maintaining excellent water quality and protecting pipelines against corrosion. Despite fluctuations in oxygen levels during system interventions, the DeOx plants have operated reliably and consistently.

VEKS has reduced operating costs by more than 50% and achieved a payback period of just five years. In addition, the improved water quality has enabled VEKS to generate additional revenue by supplying high-quality make-up water to local district heating utilities.

The proven performance of the DeOx technology has led to its adoption by several other district heating companies in Denmark. By eliminating oxygen without chemicals, BWT DeOx systems contribute to significantly extended service life of district heating networks and support sustainable, long-term operation.