As the UK heat network sector continues to evolve, there is increasing discussion around adopting the VDI approach commonly used across large parts of Europe. This represents a significant shift in how closed heating and chilled water systems are designed, maintained, and protected against corrosion.

Traditionally, in the UK, most closed systems rely on chemical inhibitors to reduce the risk of corrosion. These inhibitors act as a second line of defence by passivating metal surfaces and suppressing corrosion if, and when, oxygen enters the system. This has long been the standard approach across commercial heating and cooling systems as covered by BSRIA guidelines BG29 and BG50.

However, in many European markets operating under the VDI 2035 standard, systems are designed to operate without chemical inhibitors. Instead, they rely on higher engineering standards to minimise oxygen ingress and use much purer, low-conductivity water within the system.

The theory behind this approach is straightforward: prevent oxygen ingress from occurring in the first place while reducing the conductivity of the system water to minimise corrosion currents. But in practice, this also means that chemical-free systems can become more vulnerable if oxygen does enter the system, as there is no inhibitor present to suppress corrosion activity.

This is one of the reasons why continuous, real-time monitoring is becoming increasingly important as the UK market explores wider adoption of VDI 2035 principles.

In fact, the draft TS1 Heat Network Technical Standard highlights the importance of monitoring both chemically inhibited and chemical-free (depleted water) systems to ensure long-term system integrity and operational efficiency.

This is where Hevasure’s technology is uniquely positioned.

Unlike some monitoring solutions focused solely on chemical-free systems, Hevasure’s real- time monitoring technology supports both chemically inhibited and VDI-style chemical-free systems.

For chemically inhibited systems, our monitoring technology continuously checks that inhibitor concentration does not fall below an effective level. This ensures the system maintains its protective corrosion barrier and allows operators to intervene early if dilution or system losses occur.

For chemical-free (depleted) systems, Hevasure continuously monitors conductivity to ensure water quality remains within VDI 2035 operating parameters – typically below 100 micro-

Siemens. This is critical, as increases in conductivity can indicate contamination or changes in system conditions that increase corrosion risk.

Importantly, across both approaches, the fundamentals remain the same. Oxygen ingress, pH instability, and active corrosion remain the key threats to long-term system health.

This is why Hevasure continues to monitor critical parameters, including:
● Dissolved oxygen
● Conductivity
● pH
● Corrosion activity

By continuously analysing these parameters in real time, operators gain complete visibility into system behaviour and can identify issues before they develop into serious failures.

With over 12 years of experience and approaching 200 installations across the UK, and now in its fourth generation of product development, Hevasure has built its reputation on delivering intelligent corrosion control for real-world operating systems.

As the UK market moves towards broader adoption of VDI principles and TS1 requirements continue to evolve, the need for reliable, adaptable monitoring technology will only increase.

Hevasure is already ready for both worlds.

Whether your system uses chemical inhibitors or follows a VDI chemical-free approach, Hevasure’s real-time monitoring technology provides the visibility needed to protect system integrity, maintain compliance, and reduce corrosion risk. Contact us today to find out how we can support your heat network.