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11 Tips for optimal drinking water hygiene

Unclouded drinking water quality  

Hygienically perfect drinking water is our most important foodstuff and a basis for our health that should not be underestimated. All negative influences on the quality of our drinking water - lead, legionella, chemical and biological impurities - must therefore be avoided under all circumstances. 

1. Reasons for loss of quality

Deterioration of drinking water quality can occur, among other things due to pipeline installation, contact with unsuitable materials, stagnation in less used pipeline sections and heating. If these factors are ignored in a drinking water installation, the growth of bacteria is promoted. 

This can lead to damage to health and even endanger life and limb.

SANHA piping systems fully meet the high demands placed on the material used. Depending on the application and the quality of the drinking water, we have systems available from various types of stainless steel, copper, lead-free silicon-containing copper alloys and/or plastic which, always provide a solution that meets the requirements and guarantees optimum protection of the drinking water quality.

Besides the material used, the installation technology also plays a very important role. In addition to the correct selection of hygienic materials and system components, a system design that is coordinated with hygiene is of course a basic pre-requisite 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 far more responsible for infections than previously suspected. 

For this reason, engineers, processors and operators must increasingly focus on this "microbiological problem" in order to ensure hygienically perfect, pure drinking water at the tapping points at all times. The following explanations are intended to give the planner, the processor and the operator a general overview of the leading bacteria relevant for drinking water installations, hygienic installation methods and professional commissioning.

2. Intensive cooperation of all involved

 The importance and necessity of a responsible, continuous and intensive cooperation between planners, processors and operators is essential in the planning and execution of a drinking water installation. As a matter of course? 

Actually yes. However, the importance of cooperation cannot be emphasized often enough, because not only does a lot of attention have to be paid, but there is also a lot at stake.

Everybody knows the phenomenon: all those involved actually work well together, but when it comes to a section or sub-project, everyone assumes that the other person is responsible or cares - and then nobody cares. This is easy to avoid - and everyone, whether planner, installer, construction manager or client, should be aware of this in advance. After all, the German Infection Protection Act (IfSG) stipulates that "water for human consumption must be of such quality that its consumption or use does not cause any harm to human health, particularly through pathogens". The installation includes not only the pipes and fittings, but also the shut-off valves, water storage tanks, taps, fittings and much more. It is a matter of the correct type of installation (e.g. loop installation with double wall panels), the guarantee of sufficiently high temperatures during operation, the observance of a minimum period for water exchange, geodetic height, simultaneity factor, etc. and the responsibility for this lies primarily with the plumber and the designer. 

3. Lead bacteria for the assessment of drinking water quality

Legionella under the microscope, stained green in order to ensure a high quality of drinking water even down to the last tap, preventive measures or tests during use are now used in addition to new installation concepts for pipelines. These include testing for bacteria. Especially bacteria and germs in drinking water can lead to health problems.

From a size of 400 l, the drinking water system must therefore also be checked at certain intervals. Among the most important leading bacteria are:

Legionella

The bacterium Pseudomonas aeruginosa is the most important pathogen transmitted through drinking water.

This bacterium finds optimal growth conditions at temperatures between 25 and 30 °C. In a water analysis, none of these pathogens may occur in 100 ml of water. The Robert Koch Institute has already classified even the smallest amounts of this pathogen as "hazardous to health". 

Once an infection with this pathogen has occurred, it is very difficult to treat and can lead to serious organ diseases in humans, sometimes even resulting in death. If a drinking water system is infested with this pathogen, it is usually necessary to close the building immediately and to completely renovate the entire drinking water installation. 

E. coli bacteria  

This bacterium occurs in the human and animal intestines; it does not belong in drinking water. However, there are repeated reports of contamination. Especially in rural areas with high agricultural use, it can be introduced into the groundwater. The bacterium causes gastrointestinal complications, appendicitis and peritonitis, among others. Another faecal germ, the enterococci, has a very similar effect - they also have a particularly long life. 

Pseudomonads 

This bacterium is a cold-water germ. Particularly badly or rarely flowed through pipe sections can be infested. These occur in incorrectly planned or older pipe systems (stagnation). Dangers: Pneumonia or urinary tract infections. 

Biofilm 

Biofilms are not a bacterium or single germ, but a layer that provides food for other organisms. Therefore, there is no limit for biofilms, but only for certain germs. They form in a very short time in every pipeline. 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 water temperature. However, they also favour the implantation of health-endangering bacteria such as Legionella (see above). 

4. Danger of legionella

In Germany, it is assumed that about 3000 deaths per year can be attributed to the legionnaires' disease caused by the bacterium Legionella pneumophila. There is a risk of infection especially when inhaling aerosols (air/water mixtures), which are always present in public and private shower areas and whirlpool facilities. To prevent or eliminate this pathogen, it is important that the drinking water can be heated up to at least 70 °C for a certain period of time. DVGW worksheet W 551 describes measures for preventing and eliminating these bacteria. If this pathogen is detected in a drinking water system, elimination by thermal disinfection is usually very well possible. In this case, the drinking water must be heated up to a temperature between 70 and 95 °C. The heated drinking water must reach every part of the system. 

5. (Organic) materials in drinking water systems

The selection of the piping system, measures for hygiene during installation and expert knowledge during the installation work are indispensable in order to prevent bacteria in the pipeline network from being supplied with additional nutrients. The materials used play an important role. The materials used in the pipelines can release nutrients in the form of organic carbon compounds (DOC = dissolved organic carbon). These also contribute to bacterial growth. The Federal Environment Agency (UBA) takes this into account in its publications on the hygiene assessment of materials that come into contact with drinking water. The following UBA guidelines and recommendations were published here:

  • KTW guidelines, which contain hygiene requirements for plastics and silicones 
  • Coating guideline
  • Elastomer Guidelines

Lubricant guidelines as well as the Minority Guidelines are used to evaluate substances that occur in small quantities and do not normally enter drinking water. This includes catalysts and initiators, surface treatment of yarns and fabrics, solvents for additives and other auxiliary materials. 

The KTW guideline will be replaced by the "Basis for the evaluation of plastics and other organic materials in contact with drinking water" as of March 21, 2021. However, due to the COVID 19 pandemic, the transitional provisions have been extended by two years. The UBA's assessment basis for metallic materials is already binding. 

Especially 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 gaskets therefore undergo regular chemical and microbiological testing at the MPA Dortmund in accordance with DVGW Code of Practice W 270. 

This ensures that only the highest quality materials are used in SANHA installation systems and that there is no negative impact on drinking water quality.   

6. Optimal materials & systems

Double wall disc, lead-free copper alloy, with two press ends 

SANHA offers the materials and fittings for every application and drinking water quality that enable installers and planners to realise hygienic, durable, environmentally friendly and sustainable drinking water installations. In addition to our proven piping systems made of stainless steel, copper and plastic, we also offer various piping systems with press and transition fittings made of high-quality lead-free silicon bronze (CuSi). 

As is well known, the best installation avoids stagnation (see also points 8 and 9). Planners and installers have many fittings and connection options available for a stagnation-free (or low stagnation) installation: 

  • Favourable flow bends, 
  • Tee-pieces and threaded transition connectors,  
  • Wall angles or wall plates, 
  • Double wall plates made of the premium material CuSi and stainless steel 

This makes it easy to perform a hygienic loop installation with low pressure loss. All fittings are equipped with the appropriate press, thread or plug ends and can be connected directly to stainless steel, copper or plastic composite pipes, which ensures a cost-effective, safe and efficient installation. Especially our double-walled disks made of CuSi offer a clean and safe solution, which is ideal for drinking water installations not only due to its particularly high dezincification capability but also due to the lead-free material. 

7. Lead-free drinking water installation

The metal lead does not belong in drinking water. What does not contain lead does not release lead into drinking water. Unlike red or yellow brass which, have trace amounts of lead SANHA offers various system fittings made of lead-free silicon bronze CuSi. Today, retailers, installers and planners can choose from several series: Whether system press fittings of the 8000 "PURAPRESS" series, proven threaded fittings of the 3000 "PURAFIT®" series or system press and push fittings of the 23000, 25000 and 35000 "3fit®-Press" and "3fit®-Push" series for high-quality multi-layer composite pipes - with the lead-free systems you have it in your hands to reduce the contamination of our drinking water, after all the number one foodstuff, to zero. 

All our lead-free systems or the premium copper alloy CuSi are of course certified by the DVGW and ETA as well as many other important international certification bodies (e.g. WRAS, KIWA-ATA, CSTB, ETA, SINTEF). Our declaration to the ZVSHK ("ZVSHK Manufacturer's Declaration") also proves the perfect suitability of many of our systems for drinking water. Lead-free silicon bronze is also suitable for contact with drinking water according to the "Positive List of Materials Suitable for Drinking Water Hygiene" issued by the German Federal Environment Agency (UBA) in September 2013.

8. Reduction of stagnation times

Due to its general use, stagnation times in drinking water installations can never be completely avoided but can be minimized if the pipelines and object connections are correctly dimensioned and arranged. For this purpose, it is important to dimension the piping system according to requirements, so that already during normal operation a sufficient change of the water in the system can take place. The prerequisite for this is an exact pipe network calculation considering the actual individual resistances and a predetermined simultaneity factor [1] adapted to the user behaviour.

9. Loop and ring pipe

A "Tee-installation" should be avoided if possible; instead, the tapping points should be connected in "loop" form if possible. Regularly used tapping points should then be arranged at the end of this loop installation, or the entire floor line should be designed as a "ring line". The combination of SANHA installation systems with shut-off, control and flushing valves always guarantees a complete solution. These installation methods ensure excellent water distribution in the floor pipes by means of flexible pipe laying with few connections, while at the same time minimizing stagnation times to the greatest possible extent. 

With "loop/ring line installation", the piping is laid in a constant pipe dimension. Thermal disinfection, where a minimum temperature of 70 °C is prescribed at all tapping points, is also much easier with these installation methods. Even in systems (e.g. in hospitals), in which an additional disinfection of the drinking water pipe is prescribed, it can be ensured with considerably less effort by loop or loop/ring pipe installation that the disinfectant reaches each tapping point and also the subsequent flushing to be carried out requires less effort with these installation methods. 

10. The hygienically perfect leak detection

As in the planning and installation of drinking water systems, the leakage/pressure test must be carried out with absolute hygiene awareness. Regulations and recommendations for a hygienic leak test are provided in the ZVSHK leaflet "Leak test of drinking water installations" and BHKS rule 5.001 "Pressure test of drinking water pipes". 

This clearly states that a leak test with water must not be carried out if longer stagnation periods are to be expected after the pressure test, pipes cannot be completely emptied, pipes cannot be pressed with water due to the effect of frost, pipes must be tested for reasons of construction progress but cannot be put into operation afterwards. 

11. Leak test with compressed air or inert gas

If one assumes that a leak test must usually be carried out so that the pipes can be finally insulated and the recesses can be closed, a longer stagnation phase following the leak test can generally be assumed, even in the case of a single-family house. A hygienically perfect leak 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 must be carried out in two steps, namely the leak test (preliminary test) and the subsequent strength test (main test). The leak test is performed with a test pressure of 15 kPa (150 mbar). The test time is at least 120 minutes up to 100 litres of line volume. The test time is extended by 20 minutes for each additional 100 litres of line volume. The pressure gauges used must be calibrated and allow a reading accuracy of 0.1 kPa (1 mbar). The strength test is carried out at 300 kPa (3000 mbar) up to a pipe dimension of DN 50 inclusive. For pipe dimensions larger than DN 50, the test pressure shall be 100 kPa (1000 mbar). The test duration is 10 minutes - during this time no pressure drop must be detectable. The pressure gauges used for this test must also be calibrated and allow a reading accuracy of 0.1 kPa (1 mbar). 

 1] The basic idea behind the simultaneity factor is that peak demand is not called up simultaneously in all residential units.