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Drinking water hygiene in mixed-use properties and apartment buildings: a duty of care for both operators and tenants

In urban areas, where residential and commercial spaces are often housed under one roof, maintaining drinking water hygiene can be a particularly difficult challenge. Both the operators and tenants of mixed-use properties and apartment buildings have a key responsibility here, and must comply with certain legal duties. Only the responsible-minded actions of all parties concerned will ensure that the drinking water in the building is always maintained in a safe and hygienic condition.

For building operators, these are the 4 most important duties for maintaining drinking water quality..
These are the duties for tenants.
Tips for operators of mixed-use properties and residential buildings.
Summary: drinking water hygiene is maintained only if everyone fulfils their duties.

The 4 key duties for building operators

The property owner is responsible for ensuring that the drinking water installation, when used adequately by building tenants, is a system that is capable of supplying safe drinking water to any tapping point. Accordingly, it makes sense to incorporate this water exchange duty into the tenancy agreement.

Key duties for the building operator:

  1. Establishing the technical basis for a hygienic drinking water installation
  2. Ensuring regular testing of water quality
  3. Setting up suitable sampling points
  4. Notifying tenants if limit values are exceeded
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1. Providing a drinking water installation that is safe to use

Maintaining the quality of drinking water in a building begins with the planning of the installation. Operators must take steps to ensure that this is planned and operated in a ways that facilitates ‘specified normal operation’, i.e. a complete exchange of water occurring at each usage point in the drinking water installation by drawing-off within a maximum of 72 hours. To make this exchange of water easier, the drinking water installation should be kept ‘lean’, i.e. designed with as few surfaces as possible and with as small a water volume as possible. T-piece installations with clearly defined flow paths are also preferable. If specified normal operation cannot be achieved by means of normal usage, appropriate technical or organisational measures must be implemented. These can include the installation of a water management system, the use of SCHELL Bluetooth® modules or manual flushing procedures.

2. Mandatory inspections

To check drinking water quality for the presence of Legionella, operators must have systemic testing carried out at regular intervals. This kind of testing is explained by the Federal Environment Agency: “The term ‘systemic’ highlights the fact that the aim for such testing is not to confirm the absence of Legionella at all local tapping points but rather to monitor the drinking water installation as a whole. Accordingly, the goal is to confirm potential contamination with Legionella in parts of the drinking water installation that can affect a larger number of tapping points. This is particularly true of the central parts of the drinking water installation, such as drinking water heating systems, distributors, riser sections and circulation lines.” This is also the rationale for the procedure used when sampling residential buildings, which often differs to those used by labs. The approach for this systemic sampling as per section 31 of the German Drinking Water Regulation (TrinkwV) ‘Inspection duties relating to Legionella spec.’ is thus to sample peripheral areas instead of as close as possible to the potable water hot (PWH) riser section – which often has expensive consequences for the owner. Accordingly, building owners should set this out clearly when commissioning a testing body and explain that the building sampling should be carried out exactly according to the ‘systemic test’ specifications from the TrinkwV. Testing can be conveniently carried out using sampling valves under the wash basin and not via the corresponding sampling fitting. For Legionella testing, the applicable technical action value is 100 colony-forming units (CFU) per 100 ml. If this limit is reached, other activities become necessary, such as a risk assessment according to section 51 of the TrinkwV.

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3. Preparing suitable sampling points

To ensure precise sampling and analysis of the drinking water, building operators must take the necessary steps to prepare suitable sampling points. Section 41(4) of the TrinkwV states that these must be representative for the drinking water installation and suitable according to generally recognised codes of practice. For the reliable detection of systemic contamination, these should be easily accessible and placed as close as possible to representative riser sections. Sampling valves are available as a combined part with the regulating angle valve but also as a simple retrofit to a closed regulating angle valve.

4. Duty to notify

Operators of mixed-use properties or residential buildings are obliged by law to inform their tenants promptly when legal limits have been exceeded. This is important, as it gives tenants with pre-existing conditions the chance to take steps to protect themselves or seek medical advice. This kind of transparency is decisive for maintaining tenant trust and minimising health risks.

The 2 key duties for tenants

Tenants are also assigned some key responsibilities for maintaining drinking water hygiene in their apartment or business premises. They must…

  1. ensure a regular exchange of water every 72 hours
  2. avoid localised contamination
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1. Regular exchange of water

The regular exchange of water is one of the most important duties for tenants. As per VDI 6023 Part 1, a full exchange of water across all tapping points should occur after no more than 72 hours. Water left to stagnate in the piping for too long is the ideal environment for the excessive spread of Legionella and other pathogens. This precaution to protect health is estimated to cost around EUR 1 per month.

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2. Avoidance of localised contamination

Although building operators will be held culpable for failing to prevent the systemic contamination of the drinking water installation, tenants are responsible for preventing localised contamination. The Federal Environment Agency defines localised contamination as “the colonisation of a single outlet valve with Legionella (e.g. a single shower head or shower hose).” Although the impact of a localised contamination on neighbouring outlet valves or parts of the drinking water installation is limited, tenants should nonetheless focus on keeping tapping points clean and hygienic, both for their own safety and that of other users.

Tip for building operators: include duties in the tenancy agreement

Operators should ensure tenants are fully informed about the topic of drinking water hygiene from the outset and made aware of their duties. A prudent approach is to include a clause in the tenancy agreement that requires every tenant to carry out a regular and full exchange of water. This creates clarity and helps to avoid conflicts.

Summary

Maintaining drinking water hygiene in a mixed-use property or apartment building is a shared task whose success is crucially dependent on cooperation between building operators and tenants. Landlords must create the required technical conditions and have the water quality tested, while tenants contribute to the maintenance of drinking water quality by ensuring the regular use of tapping points. Clarity of communication and compliance with legal requirements are also decisive, in order to protect the health of all residents and users.

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