For most people in industrialised countries, drinking water hygiene is taken for granted. But is that really the case? Maintaining the high standards of the public supply network throughout a building’s plumbing system depends on the interplay between the drinking water system, the choice of materials and how the system is operated. This is because responsibility shifts at the point where the supply enters the building. From this point onwards, it is the responsibility of building services engineers, specialist tradespeople and operators to guarantee drinking water hygiene.
However, if fluctuating usage patterns and the risk of stagnation arise during a building’s subsequent operation, purely regulatory planning often falls short. This is all the more true against the backdrop of impending stricter European directives. Therefore, ensuring that drinking water remains in a flawless, hygienic condition at all times becomes a complex systemic task.
The practical definition of water hygiene in building services engineering encompasses all structural, architectural and operational measures designed to prevent contamination of the drinking water system. Whilst drinking water quality refers to the actual condition at the point of use, as determined by laboratory analysis, drinking water hygiene constitutes the technical and organisational framework that ensures this condition is maintained throughout the entire building.
The regulatory environment for building services engineers is complex. There is no single standard governing drinking water hygiene. Instead, designers and operators must navigate a web of international strategies, European guidelines and national implementation rules. The trend is clearly moving in one direction: away from purely end-point monitoring towards a holistic, preventive approach. In planning practice, the correct allocation of responsibilities is key. The WHO provides the preventive management approach, the EU sets the framework for water quality and materials in contact with drinking water, and national regulations translate these requirements into planning, execution, operation and testing.
| Regulations / Source | Significance for drinking water hygiene | |
| Global | The World Health Organisation’s concept describes drinking water safety as preventive risk management along the entire supply chain – from the source to the point of use. Risks are systematically analysed, assessed and reduced through technical and organisational barriers. | |
| Europe | The EU Drinking Water Directive enshrines the risk-based approach in European law and focuses on domestic distribution systems and materials in contact with drinking water. DIN EN 806 sets out requirements for drinking water installations in buildings. DIN EN 1717 regulates the protection of drinking water against contamination, in particular from backflow. |
The reliability of a distribution network is determined at the design stage. In the early phases of a project, utilisation models often appear straightforward, but the reality of subsequent operation is highly dynamic. Pipeline design must therefore directly factor in variables such as partial occupancy in office buildings, fluctuating booking rates in hotels, or temporary closures in educational establishments to ensure drinking water hygiene.
Hydraulic guidelines must be followed to ensure the necessary water exchange. Pipes must not be oversized for safety reasons. Large pipe cross-sections result in long residence times when flow rates are low. Furthermore, the system architecture requires the elimination of dead spaces and unused branch pipes. An isometric drawing of a pipework system helps to maintain an overview in these complex building services models. It provides the geometric basis for tracing flow paths and setting up hydraulic calculations accurately in a digital format.
However, these designs for building plumbing systems aimed at ensuring drinking water hygiene lose their effectiveness if errors occur during installation. If dust, moisture or particulate contaminants enter the system through unsealed pipe ends during the installation phase, the system is already compromised before pressure testing. Adherence to installation hygiene standards is the physical prerequisite for subsequent operation in accordance with the relevant standards.
System risks in building services engineering almost never arise from a single source of error. They result from a combination of structural, hydraulic and thermal deviations. Three risk factors are particularly common:
Stagnation occurs where water is not regularly replaced. In drinking water systems, this primarily affects oversized pipes, rarely used taps, disused building wings or sections of pipework that have remained in the network following alterations. As the residence time increases, the environment within the pipework changes: temperature, contact with materials, deposits and existing microorganisms have a longer-lasting effect on the water.
At the same time, the temperature within the pipework network can shift. Cold-water pipes can heat up in narrow service shafts, for example due to adjacent heating, hot-water or circulation pipes. Conversely, hot water can lose temperature if circulation does not reliably reach certain areas or if a pump is not functioning properly. Particularly in larger buildings, this results in zones that are still hydraulically connected but are no longer properly thermally controlled.
Biofilm constitutes the third level of this risk. It forms on surfaces in contact with water and can provide both protection and nutrients for microorganisms. Long dwell times, lack of flow and unfavourable temperatures can promote its formation on the inner walls of pipes. In such an environment, pathogens such as Legionella can multiply in drinking water.
Drinking water hygiene testing, whether mandated by the authorities or initiated internally, serves as a regulatory monitoring tool. As a microbiological and chemical analysis, it provides indicators of the system’s current condition. It reveals whether water samples taken at the tested locations show any abnormalities, but it always remains a snapshot of a specific point in time.
A normal result therefore does not exempt the system from routine maintenance measures. If, on the other hand, a water sample exceeds limit values, the actual technical analysis begins. The cause often lies deeper within the system: in architectural design flaws, unbalanced hydraulics or usage patterns that deviate from design assumptions.
In day-to-day practice, system documentation therefore becomes the most important tool. Updated pipe diagrams, validated flushing records and detailed maintenance logs enable technicians to assign laboratory findings to specific pipe sections. Only this attribution reveals whether a finding is due to stagnation, temperature shifts, insufficient flow, maintenance deficits or subsequent modifications to the drinking water installation.
The choice of materials used in installations has a fundamental impact on water quality. Technical regulations and hygiene assessment criteria for drinking water hygiene require that materials do not promote microbial growth and do not release any undesirable substances into tap water.
To minimise risks, the European Union is standardising the requirements. From 31 December 2026, a harmonised legal framework for materials and products in contact with drinking water will come into force. For new installations and repairs, EU compliance will therefore become a key planning and procurement criterion in the international building services engineering sector.
Against this regulatory backdrop, pipework systems made from high-quality polypropylene, such as aquatherm green, offer a robust technical solution. The integrated PP-R pipework system seamlessly combines pipes, fittings, adapters and specialist tools. The fusiolen® PP-R material is characterised by specific material advantages that meet the requirements for drinking water hygiene.
When the relevant pipe classes are designed to meet pressure and temperature requirements during the pipe network calculations, this establishes the technical foundation for a durable supply network. Connection technology plays a key role in ensuring hygienic design. In the PP welding process, the plastic pipe and fitting are thermally bonded to form a material-bonded unit. With welded pipe-fitting connections, no O-rings, solder or adhesives are required in the water flow. This results in smooth, material-bonded connections.
In building services engineering, drinking water hygiene has evolved from a matter of testing and maintenance alone into a discipline of risk management. Increasing European regulation and the establishment of preventive approaches such as Water Safety Planning make it clear that buildings must be designed as technical systems whose actual usage is constantly changing.
Data-driven network sizing, strict adherence to temperature limits and corrosion-free pipework systems form the foundation for drinking water hygiene in building installations. For project developers, design engineers and operators, this means that incorporating drinking water hygiene into forward-looking planning minimises regulatory liability risks and ensures the technical functionality of a property throughout its entire life cycle.
Are you facing the challenge of ensuring that drinking water hygiene in your project complies with standards and is audit-proof? The experts at aquatherm are here to support you with their in-depth expertise, from system design right through to implementation during the construction phase.
Arrange a consultation with aquatherm now.
