Hygiene planning for pressure booster systems: What you should know

Hygiene planning for pressure booster systems: What you should know

Today’s western industrialised countries take reliable and uncomplicated access to clean drinking water for granted. But we know that maintaining and further developing this convenience actually requires significant technical, regulatory and operational efforts. As legal requirements for water supply are extremely stringent, engineering contractors are obliged to consider a whole host of hygiene factors when planning and installing pressure booster systems.

Regulations, standards and laws relating to drinking water – an overview

When considering hygiene requirements, a distinction should be made between systems handling drinking water and those handling service water. According to the Drinking Water Ordinance drinking water is “water for human consumption and use.” It is water in its original condition or after treatment which is used for drinking, cooking, preparing meals and beverages, for personal hygiene and for the cleaning of objects which are destined to be used with food and those which will be in contact with the human body for any period of time. The essential requirements for drinking water quality are laid down in:

• DIN 2000 Central drinking water supply
• DIN 2001 Private and individual drinking water supply
• IfSG German Protection Against Infection Act
• LFGB German Foodstuffs, Commodities and Feed Code
• TrinkwV German Drinking Water Ordinance

The regulations for adequate water provision to consumer installations (which are applicable to units situated in buildings and property) are as follows:

• AVBWasserV German General Water Supply Terms Ordinance
• DIN EN 805 Water supply – Requirements for systems and components outside buildings
• DIN EN 806 Specifications for installations inside buildings conveying water for human consumption, and the national supplementary standards DIN 1988-200/-300/-500/-600.

Hygiene requirements to be met by pressure booster systems in building services

Wherever the minimum supply pressure (SPLN) provided by the local water supply company is insufficient to ensure that even the upper floors are supplied with adequate water pressure, the use of a pressure booster system (PBS) is necessary. As a rule of thumb, the minimum supply pressure of 2 to 3.5 bar usually provided by the municipal waterworks is sufficient for four-storey buildings. For this reason, pressure booster systems are often used in high-rise buildings. But due to water meters, filters and water treatment systems leading to water pressure losses, PBSs are increasingly being installed in residential buildings with fewer floors.

During system planning, engineering contractors should always bear in mind that their supply company can only guarantee drinking water quality in accordance with the Drinking Water Ordinance up to the hand-over point. From this point on, the system operator’s drinking water installation essentially serves to “package” the drinking water until it reaches the consumer. This means that all drinking water pipes, installed pumps and valves must not under any circumstances impair the quality of the water.

To ensure this, it is first of all necessary that all materials and auxiliary materials used in the construction of a pressure booster system (PBS) comply with the relevant regulations regarding drinking water suitability. Cleanliness during construction, transport, installation and commissioning of a PBS and all of its associated components are mandatory requirements for handling water in accordance with DIN 2000.

In order for a PBS to be operated hygienically, the PBS itself and the downstream piping up to the taps/fittings must be thoroughly flushed in accordance with DIN EN 806-4 during commissioning. Detailed information on this process is provided in the ZVSHK technical instruction leaflet “Flushing, disinfection and commissioning”. Before starting the PBS and flushing the drinking water installation, the system must be disconnected from the piping system on the pressure side and flushed separately. The flushing water must be discharged via the drainage system and any contact with the drinking water installation must be prevented.

Hazards of contamination during pressure booster system operation

Pressure booster systems (PBS) must of course also offer many years of operation without this having a negative impact on water quality. They must therefore be operated and maintained in such a way that the growth or formation of biofilms or microorganisms is minimised (see also VDI 6023):

To ensure this, drinking water stagnation or unnecessary storage should be avoided, as should temperature ranges promoting bacterial growth.

The risk of water stagnation or storage can be reduced by taking the following measures:

• Direct-flow membrane-type accumulators
• Automatic switchover between all pumps
• Smallest possible dead spaces in all components handling water
• Forced flushing of pipe sections where stagnation could occur

Water temperature also plays a decisive role in hygiene

Various factors can lead to a temperature increase of the water inside PBS components such as break tanks, pumps, pipe components and membrane-type accumulators, thus contributing to the formation of bacteria. These include increased ambient temperature at the place of installation, long periods of minimum consumption (e.g. office buildings at weekends) or also temperature increase due to the pumping operation (heat losses). However, these factors can be eliminated through the selection of an appropriate location and the prompt stopping of pumps at minimum or zero consumption.

Checklist: The five most critical points for the hygienic operation of PBSs

1. Avoid stagnation: Stagnation in the water system can promote bacterial growth.
2. Check the pressure: The pressure in the booster system should be set to ensure it is not too high. Excessive pressure can cause damage to the pipes and release bacteria.
3. Have the system serviced regularly: Professional inspection of the system is crucial to ensure that it functions properly and is operated hygienically.
4. Disinfection: Regular disinfection of the system can prevent bacterial growth. UV disinfection systems or chlorination, for example, are suitable for this purpose.
5. Filtration: Installing suitable filters can improve water quality and reduce bacterial growth.

As you can see: In terms of hygiene, there is a lot to take into account when planning a building’s water supply. It is therefore essential to consult an expert who can advise on the design, installation and maintenance of a pressure booster system to ensure that all necessary hygiene measures are taken into account.

Contact KSB’s experts if you have any questions, or discover the KSBuilding Consult selection tool for consultants which supports you throughout the entire planning process – from the draft phase via tenders right through to cost calculations.

Please contact us – we look forward to hearing from you.