Hidden Costs of Poor Water Quality: Ensuring Reliable, Low-Carbon Heat Delivery

23rd May 2023

Heat networks, or district heating systems, are a relatively new approach to delivering heat to domestic and commercial premises across the UK. Heat is generated from a central source and delivered to multiple locations through networks of pipework carrying hot water. This approach avoids the need for individual heating appliances and offers a quick route to mass low-carbon deployment.

Poor water quality can be a cause of system failures, however, there is a general lack of understanding among system operators and facilities managers about how best to monitor and maintain district heating systems.

Planned preventative maintenance (PPM) and corrosion monitoring are key strategies, leading to sustainable return-on-investment and continued growth of new low-carbon networks, together with reliability of supply and low-costs for end users.

Growth of heat networks

District heating is expected to play a significant role in Net Zero 2050 as it offers great potential to incorporate low temperature systems, such as heat pumps, as well as energy from waste facilities and industrial processes, geothermal sources and renewables. According to government research, heat networks could meet 14-20% of heat demand by 2030, increasing to 43% by 2050.

There are around 17,000 UK-based heat networks serving close to half a million consumers, 90% of whom are domestic residents. In a changing energy landscape with high energy costs and shift towards low-carbon energy, heat networks have been adopted by social housing providers as a way of delivering responsible low-impact, low-cost heating to tenants.

Poor water quality – what’s the problem?

Research published in CIBSE Journal in 2019 by Jon Greaves, Managing Director of Hydro X Water Treatment and WCS Water Division, revealed that 15% of heat networks had suffered failures because of water quality issues.

The study of 185 heat networks over a 2-year period identified specific issues leading to system failures, including:

  • Poor system water quality at handover – 12 incidents
  • Systems handed over with disused plant still connected to system – 6 incidents
  • Loss of system water (non-corrosion related) – 4 incidents
  • Full loss of system water (corrosion/scaling related) – 4 incidents
  • Full loss of system water (bacteria related) – 2 incidents

Before total failure, poor water quality can cause severe operational issues, including regular leaks and poor efficiency, increased replacement/remedial costs, reduced overall lifetime of valuable plant and equipment and high costs for service users.

Continuity of water treatment and remote monitoring technology during the pre-commission and design phase, as well as for ongoing management, would have prevented many of the failures highlighted in the study. In conclusion, Greaves recommends that “continuous monitoring and automatic dosing should be installed on all district heating networks to minimise the risk of corrosion and associated water treatment issues.”

The oxygen-corrosion connection

Oxygen is the primary cause of operational issues in heat networks.

As observed in the Greaves research, the addition of makeup water to compensate for losses leads to increased oxygen levels and risk of corrosion. Fouling of the heat exchanger reduces heat transfer and build-up of debris and scale degrades pipework and components, that will eventually lead to air ingress – and the vicious cycle continues.

Low pressure is another common cause of air ingress; positive (but not excessive) pressures must be maintained to prevent air being drawn in. Pressure sensors measure flow rates and pressures, but more effective approach is remote monitoring technology, that tracks system pressure and other precursors to corrosion in real-time and provides instant notification when water conditions change.

Preventing corrosion in heat networks

Real-time HVAC monitoring is the only way to detect the early signs of corrosion, allowing system providers and FMs to make informed service interventions that reduce the risk of downtime and protect valuable plant and equipment.

We use Hevasure’s patented water quality and corrosion monitoring technology as part of our BG50i Water Treatment & Monitoring package; a fully integrated system that incorporates a wide range of high-quality sensors connected to a sophisticated data acquisition system.

The Hevasure unit can be installed short or long-term, during the pre-commission stage or as an ongoing management tool. It remotely monitors water condition and corrosion rates, alerting users immediately if readings are out of specification.

With real-time data to hand and alarms sent direct, heat network operators can improve water quality outcomes, minimise the risk of downtime and unexpected costs, and ensure that this important technology is meeting its potential to deliver low-carbon, low-cost heat on a mass scale.

Guardian’s BG50i Intelligent Water Monitoring & Treatment package is the ideal approach to managing and maintaining heat networks and other closed-system water-based HVAC systems. For more information, click here.