Maintenance matters
As HVAC systems become more complex and facilities teams are asked to do more with less, water treatment decisions must consider operational realities as well as technical performance. Glenn Simpson, UK Manager at Enwa Water Technology UK, explores why consideration of the maintenance burden should be part of the specification process.
Water quality remains fundamental to HVAC system performance. Suspended solids, corrosion by-products, scale and biological contamination can reduce heat transfer, increase pumping energy and shorten the life of critical components.
And as low carbon heating and cooling systems adopt lower flow rates, smaller pipework and more sophisticated control equipment, maintaining water quality is becoming increasingly important. However, the challenge is not simply achieving good water quality at commissioning but maintaining those conditions throughout the operational life of the building.
Historically, water treatment strategies have often been assessed primarily (and understandably) on their ability to remove contaminants and protect system components. While these remain essential objectives, there is another factor that deserves greater attention: how the chosen filtration method will be managed over the next five to 10 years.
It’s becoming a pressing issue as facilities teams are expected to maintain today’s complex estates with limited resources. Whether operating a university campus, hospital, commercial office portfolio or district heating network, engineers are often responsible for more equipment, more systems and more data than ever before.
In this environment, maintenance requirements are just as important as filtration performance when selecting a water treatment strategy.
The challenge is especially evident in modern HVAC systems. Components such as pressure independent control valves, plate heat exchangers and heat interface units deliver impressive levels of efficiency and control but are significantly less tolerant of poor water quality than previous generations of equipment. Even relatively small quantities of suspended solids can affect performance, increase wear and ultimately reduce system reliability.
The question therefore becomes not only how effectively a filtration system removes contaminants, but how consistently it can continue to do so throughout its life. Different filtration technologies achieve this in different ways, and understanding the practical implications of each approach is increasingly important.
Passive inline filtration systems
Passive inline filtration systems, such as strainers and dirt separators, are widely used to protect major plant from larger debris. These solutions are effective at capturing heavier particles and preventing them from reaching pumps, heat exchangers and control equipment.
However, they are generally less effective at removing finer suspended solids and often rely on periodic manual cleaning or purging to remove collected debris. Where additional magnets are incorporated to capture magnetic particles, these too require regular inspection and cleaning. In large estates or district energy systems, this can create a substantial maintenance commitment over time.
Direct filtration
Direct filtration methods provide a more precise approach. By forcing system water through a physical barrier such as a cartridge, bag filter or fine screen, they can remove particles to a defined micron size regardless of density or magnetic properties. This makes them highly effective at removing all types of debris, corrosion by-products, rust, magnetite and other fine suspended solids that may impact modern HVAC equipment.
However, the very mechanism that makes these systems effective also creates a maintenance challenge. As debris accumulates on the filter surface, pressure drop increases and flow rates can be affected. Filters therefore require regular inspection and replacement, particularly in systems with poor initial water quality or where fine micron ratings have been selected.
Along with the time requirements, facilities teams must also consider the cost, storage and disposal of replacement filters throughout the life of the system. In some applications, selecting an extremely fine filtration level may improve particle removal but also increase intervention requirements if the filter becomes overloaded.
Depth filtration
Depth filtration adopts a different principle and is one that’s applied in Enwa’s EnwaMatic side stream technology. Rather than collecting particles on a single surface, contaminants are captured while passing through a layered media bed, creating a significantly larger surface area for particle loading. This allows fine levels of filtration to be achieved while reducing the risk of rapid blockage.
The media is typically cleaned through a backwash cycle rather than replaced, allowing it to be reused many times. Where this process is automated, the filtration system can maintain performance without the regular manual intervention associated with cartridges, bags or magnets.
This can be an advantage in larger buildings and district heating networks, where maintenance teams are already responsible for extensive plant and infrastructure. By reducing reliance on routine manual intervention, automated depth filtration systems can help ensure that the intended level of water quality is maintained consistently over time.
At the University of Edinburgh, for example, the Estates Engineering team is responsible for more than 500 buildings across five campuses, including district heating networks, cooling systems, research facilities and teaching buildings. Water treatment forms part of a wider strategy to improve efficiency and support long-term sustainability objectives.
The university’s engineering team reports that Enwa’s automated side-stream filtration has significantly reduced their use of traditional chemical treatment activities while helping maintain reliable operation across multiple systems. Monthly checks have largely replaced more time-intensive maintenance tasks, allowing engineering staff to focus on other priorities.
A similar experience can be seen at the University of Strathclyde, where a large district energy network serves research facilities, teaching spaces, student accommodation and sports buildings across a busy city-centre campus.
Here, EnwaMatic provides automated water treatment systems which operate largely in the background using self-flushing and automated cleaning processes to maintain performance while reducing the need for routine intervention. This allows engineering teams to manage a complex estate without adding to their maintenance burden.
A shift in thinking
These examples highlight a shift in thinking. The effectiveness of a water treatment strategy is no longer measured solely by what it removes from the system. It is also measured by how reliably it continues to perform year after year under real operating conditions.
The choice between filtration approaches is therefore not simply a question of particle removal efficiency. Designers and operators should also consider the practical realities of maintenance. How often will intervention be required? Does the solution generate a single use waste stream? Will components need replacing? Who will do this? Who will manage it? Can cleaning be automated?
These factors influence whole-life cost, operational resilience and the likelihood that water quality standards will be maintained over the long-term.
As HVAC systems continue to evolve, the methods used to protect them must evolve too. Making informed decisions about filtration performance and maintenance requirements is essential to delivering reliable, efficient and sustainable building performance throughout the life of the building.
