Maintaining water quality: helpful practical tips on the revised VDI 6023 Part 1

7-minute read

Drinking water installations are subject to especially strict regulations for health reasons. Compliance is now easier to achieve, thanks to the new VDI 6023 Part 1, which offers useful and practical advice on maintaining water quality in buildings In this article, we present a summary of the most relevant guidance for planners, fitters and operators, from Dr Peter Arens, SCHELL’s resident drinking water hygiene expert.

Insights from experience and new requirements for surfaces having contact with water

As before, the new version of this useful guidance covers the planning, execution, operation and maintenance of drinking water installations. More extensive information about operation and maintenance can also be found in the ‘double-part’ VDI 3810 Part 2/VDI 6023 Part 3. Once again, VDI 6023 Part 1 confirms insights obtained from research and experience: that only the exchange of water across all tapping points can truly help to maintain good water quality. “Otherwise, these would naturally be ‘dead pipes’,” Arens explains. Some of the new requirements focus on ensuring product surfaces that come into contact with water are hygienically safe. Other than this, there are three key parameters to maintain hygienically safe operation:

  • Cold water (PWC) must stay below 25 °C
  • Hot water (PWH) must be at least 55 °C
  • Full exchange of water at least every 72 h

Arens: “Operators should check these parameters either manually or by means of an automated system to avoid the excessive spread of Legionella bacteria. Prevention is always better than the cure: this is also required by the EU Drinking Water Directive which therefore recommends a Water Safety Plan throughout all member states.”

Understanding ‘specified normal operation’

Under ‘Terms’, the specified normal operation for a system is clearly defined as “operation of the drinking water installation across all tapping points, with routine inspection for proper function … while maintaining the operating conditions (usage frequency, tapping volumes, concurrencies) applied for system planning and set up.” This can include “simulated withdrawal of water (by manual or automated flushing).”

SCHELL tip: Once again, it has been clearly stated that a water exchange must occur across all tapping points so as to avoid the creation of ‘dead pipes’. “Accordingly, T-piece installations – which have always been part of the generally recognised codes of practice – should often be the first choice here, especially for reasons of cost and hygiene, while flushing stations should be avoided,” Arens advises.

Hygiene plan – the earlier the better

The hygiene plan continues to form part of maintenance planning, and includes the scope and frequency of routine inspections to check drinking water for specified parameters at designated, representative tapping points, plus flushing measures and documentation of all activities performed. 

SCHELL tip: The frequency, scope and parameters for routine inspections are specified in particular in German drinking water legislation and recommendations from the Robert Koch Institute. Such inspections rapidly identify any defects but do create lifecycle costs, even if installation users stay healthy. Arens: “However, exposing users to water containing pathogens is a criminal offence (German Drinking Water Ordinance, section 24). This is why flushing measures are also part of the hygiene plan. The client also needs to complete this at an early stage in the development project – ideally as part of the room schedule.” 

Avoiding microbial contamination – checking for relevant factors

Section 4.1 describes the most important factors influencing technical measures for maintaining water quality: 

  • Maintaining temperatures
  • Avoiding periods of stagnation
  • Use of materials that minimise or prevent the shedding of nutrients 
  • Compliance with volume flow rates envisaged in planning

All of these factors must be accounted for equally. Specified normal operation across all tapping points in accordance with the room schedule is an essential precondition for maintaining water quality. 

SCHELL tip: “Temperatures and the regular exchange of water while maintaining volume flow rates (i.e. concurrencies in accordance with specified normal operation) are the physical factors that can be both affected and measured. The SCHELL SWS Water Management System plus temperature sensors offers a straightforward and proactive approach to indirect, continuous hygiene monitoring – and even remotely, using the SMART.SWS online service,” Arens explains.

General dos and don’ts for planning 

Section 5.3 of VDI 6023 Part 1 states that all drinking water installations must be planned to contain a minimum possible volume of water (dimensioning of entire drinking water installation and length of individual supply lines). Reservoirs for later extensions should be avoided or made safe with flushing measures. 

SCHELL tip: “T-piece installations with a serial mains to connect up rarely used but essential tapping points therefore represent the hygienic optimum here. Typically, these will have 20 percent less water content, which increases the exchange of water during operations by around a fifth, and which therefore also protects cold water from heating. And they also have the smallest inner and outer surface areas,” Arens emphasises.  “These are important as a means of limiting microbial colonisation, plus heat absorption/heat losses from PWC and PWH/PWH-C.”

Minimum content requirements for the ‘room schedule’

According to section 5.3.1, a failure to exchange water for more than 72 h is considered a ‘service outage’. This must be avoided or compensated by means of technical and/or organisational measures (see VDI 3810 Part 2/VDI 6023 Part 3). 

SCHELL tip: Specific usage periods must be listed in the room schedule. As a result, building operators and planners should address this topic at an early stage. A sample room schedule is provided in VDI 3810 Part 2/VDI 6023 Part 3. 

Dimensioning requirements 

According to section 5.3.5, drinking water installations with high concurrencies and temporarily low periods of usage, such as sports facilities, should have suitable flushing plans and measures – or independent flushing systems. 

SCHELL tip: “In the case of a manual exchange of water, the required concurrencies needed for a turbulent flow can only be achieved with a very high investment in terms of personnel and time,” Arens explains. “The most cost-effective way to do this is to take an automated approach, like deploying SCHELL’s SWS Water Management System – a digital solution that allows you to execute water exchanges in ‘flush groups’ that guarantee a turbulent flow.” 

Production, transportation and storage of components and parts 

According to section 5.4.1, all of the surfaces on drinking water installation parts that will later come into contact with drinking water must be in a condition that does not endanger drinking water quality. Parts and equipment that have been tested dry – and therefore protected against microbial contamination – will always ensure that these requirements are met. If manufacturers use wet testing for their parts, suitable measures must be used to demonstrate that these products will not endanger drinking water quality. 

SCHELL tip: Planners should include a requirement for products with hygienically safe surfaces in the tender specifications. SCHELL always uses dry testing – and also pioneered this approach in the fittings manufacturing industry.

Filling the drinking water installation

Specified normal operation must start when the drinking water installation is filled ( 

SCHELL tip:Until handover, the trades on site will be responsible for managing water exchanges. “In a hospital with 800 beds, this means at least three employees are responsible for manual flushing five days a week,” says Arens, referring to common (and necessary) practice. “But SWS offers an automated approach to this exchange of water. This means the firms on site can use their tradespersons more productively.”

A useful compendium on drinking water hygiene

“The guidance in VDI 6023 Part 1 summarises hygiene-relevant aspects for the planning, installation and operation of drinking water systems, giving experts and building operators alike a good overview. The aim was never to replace the DIN or DVGW technical codes but to give practitioners a general reference work for drinking water hygiene,” explains Arens and concludes with praise for the authors: “This has once again been achieved.”

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