Take five
Alpesh Trivedi, Director at Magnetic, outlines five steps to optimising heating water in closed-loop systems – without chemical dosing.
Maintaining the quality of heating water is fundamental to the efficient operation of modern heating systems.
In biomass plants, district heating schemes and larger commercial HVAC installations, poor water quality can quickly lead to reduced heat transfer, system fouling and increased maintenance requirements.
Particles such as magnetite, corrosion by-products and mineral deposits often circulate continuously within closed-loop systems. Over time, these contaminants accumulate in heat exchangers, pumps and pipework, reducing efficiency and potentially shortening the lifespan of key components.
Historically, many operators have relied on chemical dosing regimes to control these issues. However, there is growing interest in alternative approaches that combine physical filtration, controlled water treatment and ongoing monitoring to maintain system performance without the need for continuous chemical additives.
A structured five-step heating water optimisation process provides a practical framework for restoring and maintaining water quality in the systems. By addressing contamination, water chemistry and system stability in a logical sequence, operators can significantly improve reliability and efficiency.
Step 1 – System analysis
Any optimisation programme begins with an accurate assessment of the heating water already present in the system. Key parameters such as conductivity, pH level and hardness are measured to determine whether the water meets recommended industry guidelines.
VDI 2035 is a widely recognised German technical guideline for water quality in warm-water heating systems in buildings. It is often used as a practical reference point when assessing heating water quality, particularly with regards to scale formation, corrosion risk and the general suitability of filling and top-up water.
Conductivity is an important indicator of the dissolved salt content of the system water, but it should not be treated as a standalone pass/fail criterion. Even water with relatively low conductivity can still be chemically aggressive if, for example, the proportion of chlorides or sulphates is comparatively high.
In practice, corrosion risk and long-term system stability depend on the wider operating conditions, including oxygen ingress, system tightness, material combination, refill behavior and pH control.
Where measurements fall outside these ranges, it often indicates the presence of dissolved minerals, corrosion products or accumulated debris circulating within the system. Establishing these baseline values allows engineers to determine the most appropriate treatment approach before any corrective work begins.
Step 2 – System filtration
Once the system condition is understood, the next step focuses on removing suspended contamination.
Closed-loop heating circuits frequently contain large quantities of magnetite sludge and metallic debris formed through natural corrosion processes. These particles can settle in low-flow areas or collect within heat exchangers and pumps, gradually reducing heat transfer efficiency and increasing energy consumption.
A practical solution is the use of mobile high-efficiency filtration units, which circulate system water through specialised filters capable of capturing both magnetic and non-magnetic particles. Unlike full system flushing, which can be disruptive and time-consuming, mobile filtration allows cleaning to be carried out while the system remains operational. This approach can significantly reduce sludge levels and restore cleaner water conditions throughout the installation.
Step 3 – Demineralisation and controlled system refill
After filtration, attention turns to stabilising the chemical composition of the heating water.
Where conductivity or hardness levels are too high, the system may be filled or topped up with demineralised water. In new installations this typically occurs during the initial system fill, while in existing systems it may follow cleaning and filtration.
Demineralised water contains very low levels of dissolved minerals, reducing the risk of scale formation on heat exchanger surfaces and other critical components. Controlling the mineral balance in this way helps ensure that the system operates within the recommended water quality parameters.
The term ‘demineralised’ water originates from the everyday use, and it is argued that the correct technical term is ‘deionised’ (desalinated) water, commonly referred to as demineralised water. Deionised water is produced using a mixed-bed ion exchange resin, which removes both cations and anions, resulting in water with very low ionic content and low electrical conductivity.
Step 4 – Heating water regulation and continuous protection
To maintain long-term water stability, many systems benefit from the installation of a heating water regulation or refill station. These units ensure that any additional water entering the system meets the required quality standards.
Continuous protection can also be supported by electrochemical treatment technologies installed within the system. In low-salt closed heating systems, electrochemical treatment can help reduce dissolved oxygen and support stabilisation of the pH value, thereby contributing to more favourable conditions for corrosion control. It should, however, be presented as a practical technical measure within an overall water treatment strategy, rather than as a universally prescribed solution for every system.
By combining controlled refill systems with water treatment measures, operators can maintain cleaner system conditions over time without relying on ongoing chemical dosing regimes.
Step 5 – Follow-up monitoring and analysis
The final stage of the optimisation process involves confirming that the system water has stabilised following treatment.
In many heating systems, the pH value may move over time toward a more favourable operating range. However, this development depends on several influencing factors, including water composition, system design, operating conditions and make-up water behaviour. Follow-up monitoring is therefore essential to confirm that conductivity and pH remain within the intended range.
Regular monitoring – often carried out several months after optimisation – provides additional reassurance that water chemistry remains stable and that contamination levels remain under control.
Supporting long-term system performance
Generally, one aspect that may benefit readers here is the assumption of long-term system tightness.
In practice, the degree of tightness of a ‘closed’ system is operationally dependent and can change over time. Fresh water make-up should therefore be regarded as an indicator of system deviation or fault, rather than as a normal operating condition.
Potential sources of oxygen ingress, such as pressurisation units, degassing devices, expansion vessels, membranes and polymeric pipe materials, play a critical role in system behaviour and long-term corrosion risk.
For operators of biomass plants, district heating networks and commercial heating installations, a structured optimisation programme can therefore deliver several benefits. These include improved heat transfer performance, reduced maintenance interventions and extended equipment lifespan.
For district heating and industrial heating applications, additional or alternative guidance may apply, for example AGFW FW 510 in Germany, which sets out requirements for circulation water in industrial and district heating systems and recommendations for their operation.
As the industry continues to focus on energy efficiency and sustainable operation, interest in chemical-free water treatment strategies is expected to grow. By combining careful analysis, effective filtration and controlled water management, operators can maintain high system performance while reducing reliance on traditional chemical treatment approaches.
