10 guidelines for optimal drinking water hygiene
Unclouded enjoyment of drinking water
1. Reasons for quality deterioration
A deterioration in the quality of drinking water can occur, among other things, due to the pipework installation, contact with unsuitable materials, stagnation in less frequently used sections of pipe and/or unacceptable heating. If these factors are disregarded in a drinking water installation, the growth of bacteria is encouraged.
This can lead to adverse health effects up to and including a risk to life and limb.
SANHA® piping systems fully meet the high demands placed on the materials used. Depending on the application and the characteristics of the drinking water, we offer systems made of premium stainless steel, copper, lead-free silicon-containing copper alloys and/or plastic, which always provide a needs-based solution and ensure optimum protection of drinking water quality.
In addition to the materials for fittings and pipes used in drinking water installations, the installation technique also plays a very important role. In addition to the correct selection of hygienically suitable materials and system components, a hygiene-focused system design is of course a basic prerequisite for the quality, durability and sustainability of a drinking water installation. In recent years, scientific studies have made it increasingly clear that bacteria from drinking water are responsible for far more infections than previously assumed.
Therefore, engineers, installers and operators must focus more closely on this ‘microbiological problem’ in order to ensure that hygienically impeccable, pure drinking water is always available at the points of use. The following information is intended to provide planners, installers and operators with a general overview of the indicator bacteria relevant to drinking water installations, hygienic installation methods and proper commissioning.
2. Lead-free drinking water installation
The importance of lead-free materials continues to increase due to current regulatory developments - and action is urgently needed. With the revised EU Drinking Water Directive, the new version of the ECHA list (see below) and the successive imminent adaptation of national regulations, the requirements for materials in contact with drinking water are being tightened once again. Numerous (copper) alloys previously permitted will then no longer be allowed in the drinking water sector and even placing them on the market for this purpose will not be permitted.
Planners, installers and operators must already take these requirements into account in new-build, refurbishment and modernisation projects. An early switch to suitable lead-free materials provides planning and investment certainty, avoids later retrofits and supports long-term compliance with legal requirements, after all stock rotation can take several years.
3. Indicator bacteria for assessing drinking water quality
Legionella
Coli bacterium (E. coli)
This bacterium occurs in the human and animal gut; it does not belong in drinking water. However, there are repeated reports of contamination. Especially in rural areas with intensive agricultural use, it can enter groundwater. The bacterium causes, among other things, gastrointestinal complications, appendicitis and peritonitis. A similar effect is seen with another faecal germ, enterococci – they also have an especially long survival time.
Pseudomonads
This bacterium is a cold-water germ. Pipe sections with particularly poor or infrequent flow can be affected. These occur in incorrectly designed or older pipework systems (stagnation). Risks: pneumonia or urinary tract infections.
Biofilm
Biofilms are not a bacterium or single germ, but a layer that provides nourishment for other organisms. Accordingly, there is no limit value for biofilms, only for certain germs. They form in a very short time in every pipe. They are not harmful to health in every case. On the contrary, they partly protect the inside of the pipe and even help to keep the water clean. The formation and composition of the biofilm also depends on the pH value and the water temperature. However, they also favour the colonisation of bacteria hazardous to health such as Legionella (see above).
4. (Organic) materials in drinking water installations
- KTW guidelines, which contain hygiene requirements for plastics and silicones,
- Coating guidelines
- Elastomer guidelines
Lubricant guidelines as well as the de minimis guidelines are used to assess substances that occur in small quantities and normally do not enter the drinking water. This includes catalysts and initiators, surface treatment of yarns and fabrics, solvents for additives and other auxiliaries.
As of 21 March 2021, the KTW guideline will be replaced by the "Assessment basis for plastics and other organic materials in contact with drinking water". However, due to the COVID-19 pandemic, the transitional provisions were extended by two years. The UBA's assessment basis for metallic materials is already binding.
In particular, when using organic materials, it must be ensured that they do not provide a breeding ground for microorganisms. Such organic materials include EPDM seals. All organic materials used by SANHA® for seals therefore regularly undergo the required chemical and microbiological tests in accordance with DVGW Code of Practice W 270 at MPA Dortmund.
This ensures on an ongoing basis that only materials of the highest quality are used in SANHA® installation systems and that any negative impact on drinking water quality is ruled out.
5. Optimal Materials & Systems
- flow-optimised bends,
- tees and threaded connection fittings,
- wall elbows or wall plates,
- double wall plates from the premium CuSi and stainless steel ranges
6. Intensive collaboration by all parties involved
Basically, yes. Nevertheless, the importance of cooperation cannot be emphasised often enough, since there is not only a lot to consider, but also a lot at stake.
Everyone knows the phenomenon: all parties actually work well together, yet in one section or sub-project each assumes the other is responsible or will take care of it — and then no one does. This is easy to avoid — and everyone, whether planner, installer, site manager or client, should be aware of it in advance. After all, according to the Infection Protection Act (IfSG), “Water for human consumption […] must be such that, through its ingestion or use, harm to human health, in particular from pathogens, is not to be feared.” The installation comprises not only the pipes and fittings, but also the shut-off valves, water storage tanks, the draw-off points, taps and much more. It is about the correct type of installation (e.g. loop installation with double wall plates), ensuring sufficiently high temperatures in operation, observing a minimum period for water exchange, geodetic head, simultaneity factor and much more, and those chiefly responsible for this are, above all, the installer and the planner.
Drinking Water Ordinance, DIN, DVGW, ZVSHK...
On top of that, the laws, regulations and technical rules are not always entirely easy to keep track of. In addition to the Drinking Water Ordinance and DIN EN 806, DIN EN 1717 (Protection of drinking water from contamination) applies, and in certain cases — of course not in all — national extension standards such as DIN 1988-100 to -600. There are also DVGW W rules, VDI 6023, ZVSHK information sheets, etc.
So it makes sense not to rely on one party and their elephantine memory, but quite simply to ask. Ideally, there is a written plan for this. The importance of close cooperation is also underlined by the fact that inadequate drinking water quality constitutes a criminal offence under the currently applicable Drinking Water Ordinance. Furthermore, DIN EN 806 (Technical rules for drinking water installations) stipulates that an installation for a calculated service life of 50 years must meet the functional requirements, cause no damage and must not endanger health.
Even from this alone, it follows for every type of drinking water installation — not only for hotels, catering, hospitals, care homes or similar facilities, but also in single-family homes — that the utmost care must be taken with regard to hygiene. Therefore, the same applies here: if you talk, you can be helped!
7. Reducing stagnation times
Due to normal usage, stagnation times in drinking water installations can never be completely avoided, but with correct sizing and arrangement of the pipework and terminal connections they can be minimised. To this end, it is important to size the pipework system to suit demand so that, even in normal operation, there is sufficient turnover of the water in the system. This requires an exact pipe network calculation taking into account the actual local resistances and a specified simultaneity factor adapted to user behaviour [1].
8. Loop and ring main
9. The hygienically sound leak-tightness test
It clearly stipulates that a leak-tightness test with water must not be performed if longer stagnation periods are expected after the pressure test, pipelines cannot be completely drained, pipelines cannot be pressure-tested with water due to the effects of frost, or pipelines have to be tested for reasons of construction progress but cannot then yet be put into operation.
10. Leak-tightness testing with compressed air or inert gas
Assuming that a leak-tightness test generally has to be carried out so that the pipes can be finally insulated and the recesses closed, a longer stagnation phase following the leak-tightness test must, in principle, be expected, even in a single-family house. A hygienically sound leak-tightness test is therefore only possible in the form of a “dry test” with oil-free compressed air or inert gas (nitrogen or carbon dioxide). This test is to be performed in two steps, namely the leak-tightness test (pre-test) and the subsequent strength test (main test). The leak-tightness test is carried out with a test pressure of 15 kPa (150 mbar).
The test time for a pipe volume of up to 100 litres is at least 120 minutes. For each additional 100 litres of pipe volume, the test time increases by 20 minutes. The pressure gauges used must be calibrated and allow a reading accuracy of 0.1 kPa (1 mbar). The strength test is performed up to and including a pipe size of DN 50 at 300 kPa (3000 mbar).
For pipe sizes greater than DN 50, the test pressure must be 100 kPa (1000 mbar). The test duration is 10 minutes - during this time no pressure drop may be detectable. In this test, too, the pressure gauges used must be calibrated and allow a reading accuracy of 0.1 kPa (1 mbar).
1] The basic idea of the simultaneity factor is that peak demand is not drawn in all residential units at the same time.