Untreated water can destroy a heat network in under five years. So, why is water management so often overlooked? Steve Morris, head of engineering at Insite Energy, explores the issue.
Poor water management can undermine a heat network long before a major failure becomes visible. Corrosion, sludge, limescale and debris can restrict flow, damage pumps, block strainers, clog filters, reduce heat-transfer efficiency and contribute to premature boiler and pipework failures. As well as higher energy and maintenance costs, this can mean shortened asset life, loss of heating and hot water and major disruption for residents.
Meanwhile, the launch of the Heat Network Technical Assurance Scheme (HNTAS) in 2027 heralds a significant shift in how heat network operators and suppliers are expected to manage their assets. Compliance will increasingly need to be demonstrated through measurable performance indicators, putting greater focus on how networks are operated and maintained.
Water quality is central to this. Water management must therefore now be treated as an ongoing asset-management responsibility rather than an issue to address only when a fault occurs.
Separate systems, different risks
Water quality within a heat network should not be confused with potable water safety. In multi-occupancy buildings, heating and drinking-water systems are separate, with backflow protection required to prevent cross-contamination.
Low-temperature hot water (LTHW) systems typical in heat networks are usually closed, circulating water through the network rather than supplying it for consumption. That means the risks are different, but the maintenance requirement remains important.
In Insite Energy’s mechanical compliance audits, only 15% of operators were able to provide evidence of LTHW water-quality treatment, indicating that many systems are a long way from where they need to be on managing water condition effectively.
The silent threat
The risks of damage due to poor water quality are particularly significant for older or inadequately maintained networks. A system designed to operate for 25 years can suffer severe degradation in less than five if water quality is not routinely monitored and treated.
Initially, the consequences may appear relatively minor, perhaps appearing as recurring heating problems or reduced system performance. Left unaddressed, however, they can develop into major failures, particularly during periods of high winter demand.
As heat networks use commercial-scale equipment, components can be considerably more expensive than equivalent domestic heating equipment. Over a 30-year period, the cost of prematurely replacing them far exceeds the investment needed to monitor and maintain water quality proactively.
In one recent example we came across, untreated water had contributed to pipework degradation impacting supply to 190 homes. This was costly to repair and left residents on several floors without heating for a week.
Measurement first
To avoid these type of scenarios and ensure HNTAS compliance, the first step for heat operators and suppliers is to understand the condition of their existing portfolio, undertaking a gap analysis against expected forthcoming requirements.
Data has an important role to play here. Monitoring water top-up volumes, for example, can flag any issues with pressurisation or expansion equipment and help to identify and track leaks before they cause significant damage. Similarly, household heat meters can provide a useful warning system. Any change in consumption levels should prompt an investigation.
This doesn’t always mean an immediate site visit, however. In larger networks, desktop surveys and remote analysis can often help identify the likely cause of an issue, allowing maintenance teams to prioritise problems and arrive prepared.
Planning ahead
Planned preventative maintenance (PPM) is one of the most straightforward ways operators can improve network performance while preparing for HNTAS. It also helps ensure replacement parts are procured before they’re urgently required in winter.
Water testing should form part of the routine maintenance regime, with samples sent to a laboratory for analysis on a quarterly basis. Regular circulation checks should also be carried out, together with chemical dosing, flushing and other corrective actions as needed. Strainers and filters need particular attention. Managing these components is a relatively simple intervention that can prevent blockages developing into more serious failures.
Water-quality management should be properly documented and align with industry guidance such as CIBSE CP1 (2020) and BG 50/2021.
Ensuring compliance
The coming regulatory changes make it increasingly difficult to treat water quality as an after thought. If operators are expected to demonstrate network performance through KPIs, they will need reliable maintenance records and evidence that potential causes of poor performance are being identified and addressed.
A mechanical compliance audit every one to three years can help identify risks before they escalate, while annual servicing, water testing and monitoring provide the ongoing oversight needed to protect the network.
The message for operators is straightforward: water quality is not simply an engineering detail. It affects efficiency, reliability, asset life, operating costs and resident comfort. Addressing it now is one of the practical steps that can strengthen network performance before HNTAS compliance becomes a reality.