Every year, the issue of water hygiene in our water supply systems becomes more acute. The global decrease in the availability of drinking water, groundwater pollution, deterioration of existing water supply networks and the use of hazardous materials in contact with water lead to a decrease in water quality. But next to that, even after cleaning, the risk of deterioration of water quality and its hygienic properties is quite high.First of all, it is caused by three main operational factors, the failure of which leads to bacterial and chemical contamination of water:
- stagnation of drinking water in the network of pipelines,
- an increase in the temperature of cold water and insufficiently high temperature of hot water supply,
- the use of fittings and pipes made of materials that are dangerous for humans and can lead to water pollution.
One of the problems of water supply networks is the presence of stagnant areas in the pipeline system. Stagnation occurs during long periods of non-use of water, when there is no breakdown and circulation. The issue of avoiding water stagnation has become even more urgent in light of the COVID-19 pandemic, which the whole world is currently experiencing. Quarantine measures lead to the periodic shutdown of enterprises, hotels, educational institutions and office buildings. In many cases, the use of the building or the behavior of users has changed over a certain period of time and, accordingly, the designed mode of operation of water supply systems is violated and bacterial contamination of water occurs, due to its stagnation and temperature increase in cold water supply pipelines.
The most common water contaminant is Legionella bacteria (Legionella pneumophila), which spreads best at temperatures from 25 to 55 °C in areas with stagnant water.
In a colder environment, bacteria and germs remain viable but not active, while 60 °C becomes lethal to microorganisms. For this reason, for example, storage water heaters must always operate at a temperature ≥ 60 °C. If legionella infection is detected, thermal disinfection should be carried out by raising the temperature to 70 °C. Therefore, it is recommended to use flow-through stations equipped with stainless steel heat exchangers for hot water heating as much as possible. Using the flow mode for hot water preparation allows you to avoid bacterial contamination, the appearance of unpleasant odors and reduce operating costs.
Installation shafts for cold water supply pipelines should be located in such a way that the cold water temperature does not exceed 25°C (recommendation: not higher than 20°C). Cold water pipes must be planned and constructed in such a way that they are thermally separated from hot water supply pipes. All water supply pipes must be properly insulated.
Another weapon in the fight against bacterial contamination, in addition to high temperature, is to ensure a regular flow (movement of water). Water standing in the pipe for a long period of time creates stagnant zones that are a favorable environment for the formation of colonies of bacteria and microbes. Stagnation of water contributes to the formation of a biofilm on the inner surface of the pipes, which in turn protects legionella from high temperatures and provides food and an environment for reproduction. During stagnation, the temperature of cold water can also rise above 25°C, which also creates additional risks of the formation of dangerous pathogens.
Always take into account situations where usage phases alternate with longer breaks, for example in hotels or educational institutions. However, the frequency of use depends on the consumer, which makes it difficult to predict. Therefore, the correct planning of water supply systems is crucial to ensure an appropriate level of hygiene. It is necessary to avoid terminal (dead) lines and areas with non-permanent sampling, circular water supply systems should be provided in the projects, which significantly improve the situation with regular exchange of water in pipelines. When opening the bulls of any selection point, water moves along the entire section of the ring line.
The temperature in the entire hot water network should not fall below 55°C. Since hot water can cool down during periods of no water separation, it is necessary to maintain its constant temperature by means of circulation in the hot water supply pipelines. Hydraulic balancing of the circulation system is a necessary condition for the correct functioning of the hot water supply system. A properly planned circulation system ensures that the hot water temperature never drops below 55°C at any point in the water supply.The volumetric circulation flow must be able to transport the same amount of heat that is lost through the surface of the pipeline. This means that a given water temperature can be maintained only if an equilibrium state is ensured at each point of the circulation system. Thus, hydraulic balancing of the circulation system is the main condition for the safe operation of the hot water supply system.
Balancing valves guarantee constant flow in all sections of the pipelines and ensure the necessary high temperature at the most remote points of water intake. Balancing fittings also optimize the operation of the hot water supply system during thermal disinfection of pipelines.
Let's consider some principle schemes for setting up a hot water supply system using Kemper balancing valves:
This scheme provides for the balancing of hot water recirculation risers. MULTI-THERM multifunctional valves are used, which combine several functions in one body: thermal regulation of precise volume flow, closing, draining and temperature control. MULTI-THERM not only works in the operating temperature range of 50 - 65°C, but also automatically supports thermal disinfection at temperatures > 70°C. The solution is used in the absence of a recirculation line in individual bathrooms of high-rise buildings or hotels, or for balancing individual bathrooms of a private house.
The following scheme provides hydraulic balancing of hot water recirculation risers and thermal-hydraulic balancing of each bathroom. Main lines are equipped with balancing circulation valves KEMPER MULTI-FIX-PLUS, which allow manual adjustment of exact volumetric flows based on calculated values. Next, in each bathroom, an apartment-by-apartment balancing valve ETA-THERM is installed, which ensures a constant volume flow and shuts it off when the set temperature is reached. Thus, the required temperature is guaranteed in all bathrooms and toilets. The use of such a solution ensures increased hygiene and comfort requirements and allows you to get hot water immediately after opening the tap.
Another effective solution that will help eliminate the problems of water stagnation and its inefficient change is the use of KHS Venturi flow distributors, which ensure a constant flow, a predictable volumetric flow throughout the water network and the absence of any stagnant zones. KHS Venturi dynamic flow separator can be used in cold and hot water supply systems, as well as hot water recirculation lines.
To ensure a guaranteed flow in the system and to protect water from contamination, you should use sanitary and hygienic drain installations. First of all, this applies to objects with a non-permanent or variable mode of operation, such as educational institutions, hotels, as well ashospitals, clinics or homes for the elderly, where the requirements for the safety of the water supply system are increased. The use of sanitary drains is also appropriate for country houses, especially for residences with several bathrooms. Periodic washing in hospitals, hotels, educational institutions and private houses with a significant number of bathrooms should be carried out regularly, regardless of whether these premises are used or not.
Kemper's KHS and HS2 hygienic flushes help restore the planned operation of the water supply system with a controlled drain. The water is changed according to the set parameters of time, temperature and volume.
Sanitary drain installations can be used as independent devices for washing, or combined in cascade solutions with connection to BMS (building management system) or using the KHS Mini System Control MASTER 2.0 controller, to build large-format systems. Thus, KHS and HS2 installations are equally effective for both private facilities and large projects such as hospitals, hotels or boarding houses.
One of the key factors in the successful construction of a high-quality water supply system is the use of fittings and pipes, which are made of materials safe for humans, which do not lead to water pollution or poisoning. Unfortunately, almost no attention is paid to this in our country, continuing to use materials that are very often simply dangerous for our health, such as - corroding steel pipelines; brass fittings and fittings, which have a high content of lead in their composition and in which zinc is leached; polymer pipelines that do not have a hygienic approval for use in water supply systems, etc. The use of safe materials is extremely important in the construction of water supply systems that meet the standards of hygiene and health safety. That is why in our projects we use materials and equipment that meet the requirements of the European standard EN 1717:2000 Protection against contamination of drinking water in water supply installations and general requirements for devices to prevent backflow pollution:
- Kemper stop and balancing fittings, which are made of bronze, which has high corrosion resistance and does not contain dangerous impurities. The design of Kemper valves does not contain "dead" zones where bacterial contamination could occur. And the sealing of all valves is made of EPDM, which meets the hygienic requirements of all European and national standards.
- cross-linked polyethylene pipelines, Fränkische companies meet all requirements for safe water supply. PPSU fittings and special CW742R brass are used for the connection, which is lead-free and corrosion-resistant.
- another type of pipelines used for drinking water supply - stainless steel pipes from the Geberit company. The system Geberit Mapress made of chromium molybdenum titanium stainless steel is corrosion resistant and safe to use in drinking water supply systems,
- all connections to the water supply network, such as feeding the heating system or connecting a high-pressure washer, are made through devices that prevent contamination of tap water due to backflow,
- external non-freezing faucets made of bronze, which are completely emptied after use and thus prevent the formation of stagnant zones.
Thus, the issue of designing water supply networks is the key to the correct arrangement of the cold and hot water supply system. Clear design solutions and correctly selected materials guarantee the operational and hygienic safety of your water supply. Pay primary attention to the issue of correct and high-quality design.
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