The maintenance of temperature in domestic hot water systems is an issue that concerns not only energy efficiency, but also safety and health. In the water systems of civil and industrial buildings, thermal control represents the primary line of defense against the proliferation of Legionella, a bacterium that, under certain conditions, can colonize pipes, tanks, and components of the DHW system, with serious consequences for the health of users.
Legionella in water systems: when and why it proliferates
Legionella pneumophila survives within a temperature range of 5 to 55°C, but it is between 20 and 42°C that it finds ideal conditions to multiply, especially when the inner walls of pipes contain organic deposits (biofilm), limescale buildup, or stagnant areas. Storage tanks, rarely used pipe sections, unused branches, and joints made of porous materials such as rubber are the critical points of any DHW system.
The environments most exposed to bacterial proliferation are large-scale systems and branched water networks: healthcare facilities, hotels, nursing homes, and industrial complexes that use hot water cycles. In these cases, the distance from the heat generation points and the length of the piping make it difficult to maintain uniform temperatures throughout all pipelines, creating potential risk areas.
Temperature maintenance in systems as a preventive measure
The guidelines for the prevention and control of Legionellosis issued by the Ministry of Health, also incorporated into Legislative Decree 81/2008 for workplace environments, set specific temperature thresholds: domestic hot water must be produced and stored at temperatures above 60°C and maintained during distribution and recirculation at no lower than 50°C. Below these limits, the risk of bacterial proliferation increases significantly.
Heat losses in terminal sections, nighttime shutdowns, seasonal variations, and load changes can locally lower the water temperature, even when the generator is operating correctly. Therefore, to ensure stable and compliant conditions throughout the entire network, a dedicated control system and technical solutions specifically designed ad hoc to integrate with the system infrastructure are required.
Anti-legionella treatments: types and limitations
To ensure the prevention of Legionella in water systems, there are two main categories of preventive interventions:
- Thermal treatment, or “thermal shock”, consists of raising the water temperature to above 70°C for an extended period, in order to reduce the bacterial load present in the system. It is an effective solution, but not definitive unless supported by consistent temperature maintenance. In fact, once the water cools down and enters the risk temperature range, bacterial recolonization can resume;
- Chemical treatments rely on disinfectants such as chlorine, chlorine dioxide, or hydrogen peroxide, introduced into the water system through continuous or scheduled cycles. While these active substances are useful and often included in risk management plans, they have certain limitations. In order for their concentration to be effective in counteracting the bacterial load, they must be administered with precise dosing and continuously monitored. Moreover, they can be less effective in the presence of established biofilm;
- la disinfezione con raggi UV è un’ulteriore opzione, particolarmente indicata nei punti di immissione in rete, ma non estende la sua azione lungo l’intero impianto.
The common point among all these solutions is that they act on the existing bacterial load, whereas thermal control eliminates, at the source, the conditions that favor its development. For this reason, effective prevention always starts with temperature maintenance in systems, understood as a structural, continuous, and indispensable safeguard.
Cost comparison: periodic treatments vs. a permanent solution
The various solutions for anti-legionella treatments involve different costs. The chemical approach requires the recurring purchase of disinfectants, as well as expenses related to dosage monitoring (specialized technicians, dedicated equipment), not to mention the introduction of compounds into domestic water, which we come into contact with daily. UV lamps also involve periodic maintenance and component replacement.
Heating cables, on the other hand, represent a permanent solution: once installed, they do not require repeated interventions or the consumption of materials. The initial investment pays off in the long term, reducing operating costs and ensuring continuous system autonomy without additional expenses.
Heating cables for temperature maintenance in DHW systems
In this context, heating cables represent a precise and reliable technical solution. Applied along the piping of the DHW system, they maintain a constant water temperature even in sections farthest from the generator, in secondary branches, and in historically critical points. Unlike traditional recirculation solutions, electric heat tracing operates in a localized and controlled manner, integrating thermostats and monitoring systems that regulate heat input based on the actual conditions of the system, while also eliminating the need for a return pipe and all related components such as valves, pumps, and various instruments.
Self-regulating systems, in particular, automatically adjust the power output based on the detected temperature: they deliver heat where and when it is needed, reducing energy consumption while ensuring continuous protection. For tanks and system components, the same technology allows the maintenance of thermal conditions required by regulations, even during periods of low usage or partial system shutdown.
At Parma ST, we provide technical consulting, design, and installation of Raychem heating cable systems for civil and industrial DHW systems.
Leak detection in domestic hot water systems
The plumbing system can be optimized by integrating and managing, through a single interface, both a thermal regulation system and one dedicated to monitoring water leaks. Even when not immediately visible, these leaks represent a real risk: in addition to structural damage, they promote localized stagnation and temperature drops, creating ideal conditions for bacterial proliferation.
Leak detection systems based on sensor cables continuously and automatically detect the presence of liquid along pipelines, ducts, and critical points of the system. The device signals anomalies in real time, allowing for prompt intervention before the issue spreads further. In complex systems, such as those in healthcare or hospitality facilities, continuous monitoring of this kind can make the difference between routine maintenance and an unexpected shutdown of the entire facility.
At Parma ST, we install and configure both technologies, designing tailored solutions for every operational context. Our experts support you from initial consultation and assessment through to final testing, with guarantees that go beyond market standards.
Contact us to analyze the characteristics of your system together and identify the most suitable solution.