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The storage tank systems. Ideal for commercial use.

Water is hugely versatile. It provides a whole host of options for everyday use – whether as an essential, valuable resource in kitchens or in daily use in sanitary rooms and building technology due to its ability to be stored and transferred. 
In all applications in which water comes into direct contact with the body, it must be supplied in the optimum quality and in sufficient quantities in line with stringent hygiene standards. These domestic hot water systems are subject to strict standards regarding planning, design and operation so as to ensure the reliable and hygienic supply of domestic water at the right temperature. However, if the water is to be used as a storage medium to retain energy obtained from valuable resources or to hold surplus energy, this is where system requirements come to the fore. The buffer storage tanks required decouple energy generation and energy consumption in the heating system to achieve the greatest possible system efficiency. With this technical trick, it is possible to make use of the sun’s energy even during the night, for example.


When it comes to domestic hot water, hygiene is the top priority. Given the value of water in sustaining life, Hoval domestic water systems must meet strict hygiene requirements.


With its comprehensive range of products for heating water and storing energy, Hoval offers suitable solutions for buildings ranging from blocks of flats and hotels right the way up to industrial plants.


The use of high-quality materials and an optimal component configuration ensure that the system operates in a particularly energy-saving manner and increases its overall service life.

Hygienic water heating

Water sustains life in many different ways. While the concentration of germs in natural watercourses is harmless due to the water temperature and movement, the greatest possible attention must be paid to hygiene when domestic water is heated. Building installations must be designed in such a way as to prevent the formation of biofilms in which bacteria such as legionella can grow. Legionella thrive best in stagnant water at temperatures between 32 and 42°C; however, their growth is halted at temperatures between 60 and 65°C. For this reason, the domestic hot water system should reach high temperatures on a regular basis. Electrical auxiliary heaters with no circulation pipe can carry out thermal disinfection by switching on and off automatically. However, the domestic hot water should ideally never drop below a temperature of 60°C and the water should not be allowed to stand in the pipes for long periods. Hoval domestic water systems meet all hygiene requirements and offer optimised energy efficiency.

Hygiene plays a central role for the operators of domestic hot water stations.

Which system is the best for heating water?

These days, domestic hot water systems are part of the central heating system in which the heated water transfers the heat to the domestic water. There are various ways of doing this, depending on the heating system.

Selecting and planning the right hot water system depends on multiple factors, such as domestic hot water demand, the available space, the level of convenience required, environmental protection standards, hygiene requirements, legal requirements and financial resources.

Your Hoval partner will be at your side to identify your needs and the amount of domestic hot water required and find the right domestic water heating solution.

Choosing the right storage system depends on various factors and is therefore highly individual.

How does water hardness affect my domestic hot water system?

Limescale and other deposits are not just an important issue for household appliances – they can be relevant to the domestic water system, too. Water hardness is determined by the proportion of calcium and magnesium compounds dissolved in the water: the higher this proportion is, the harder the water is. If water that is too hard is used without a suitable treatment, this can lead to corrosion which shortens the service life of the water heater and affects hygiene, as deposits such as limescale can promote the proliferation of germs.

Hoval provides various options for protecting the domestic water system, such as the use of magnesium anodes or maintenance-free impressed current anodes. Irrespective of the water hardness, Hoval will find a suitable solution to ensure the system operates perfectly.

To ensure that your system runs smoothly, it is important that you know the water hardness.

The function of a buffer storage tank

The buffer storage tank fulfils the purpose of decoupling the generation of heat from the use of heat in the heating system. This enables the heat generator to work more independently of the building’s current heat demand, preventing the system from switching on and off frequently. In addition, the buffer storage tank is ideal for incorporating a second heat source or regenerative energy, such as a solar plant, into the heating system. There are a number of benefits associated with the use of buffer storage tanks: they enable resources to be used wisely, improve operating behaviour, boost efficiency and increase the service life of the heat generator. Collectively, the use of buffer storage tanks results in increased efficiency of the overall heating system.

The purpose of the buffer storage tank is to store surplus energy or domestic hot water temporarily.

Water heating – what are the options?

A distinction is made between domestic water storage systems and continuous flow systems.

The domestic water storage system

The concept of the domestic water storage system is the traditional solution and is often referred to as a “domestic hot water storage tank” or “domestic water storage tank”. Here, cold water is first heated as a reserve, stored and discharged if needed. A heat generator such as a heat pump or a pellet, oil or gas boiler heats the cold water via a heat exchanger in the bottom section of the storage tank. If a solar plant is used in addition, the domestic hot water storage tank has an additional heating coil. Well-insulated storage tanks don’t just protect the environment – they also save money. They minimise heat loss and ensure efficient and economical operation.

Continuous flow system

Systems which use the continuous flow principle heat the cold water directly for consumption, meaning the amount of domestic hot water produced is only ever as much as is needed. This enables heat loss to be avoided and prevents the water from standing for a long period of time.
A brief explanation of the continuous flow principle: the essential element of this principle is the heat exchanger, which has two completely separate circuits. When the tap is opened, the process of heating the water starts and both circuits come into play. The cold water flows through the heat exchanger in the separate cold water circuit and absorbs the heat from the hot circuit, which flows through the heat exchanger starting from the heating system. 
Peak demands for domestic hot water are increasingly common in commercial applications in particular. In order to ensure that these demands can be met at all times, the buffer storage tank needs to be the right size to supply the heat required quickly.

Storage systems for domestic hot water: CombiVal and MultiVal

The conventional method for producing hot water involves using storage tanks that are supplied with heat from the heating system. There are a wide range of storage tanks for heating and storing domestic water. With its CombiVal product line, Hoval offers a broad portfolio of stainless steel or enamelled water heaters. There is the right product to meet every requirement. For example, calorifiers, which are ideal for use with a heat pump, have extra-large heat exchanger surface areas. The MultiVal series is specially designed for combination with a solar plant and features an additional heating coil. First-rate insulation helps to save energy, while the high-quality components ensure a long service life.

Domestic hot water continuous flow systems: TransTherm aqua F / L

Continuous flow systems with fresh water stations are different from storage tank systems as they maintain little or no reserve of domestic hot water. This prevents heated water from being stored for longer periods. The main benefit of the continuous flow principle is that sanitary rooms and the kitchen are continuously supplied with fresh and hygienic domestic hot water. With the TransTherm aqua F/L fresh water modules, Hoval has developed a powerful, compact system that requires limited space, is ready for connection and quickly supplies the domestic hot water required at any time.

The EnerVal heat and cold buffer storage tank

The EnerVal buffer storage tank is filled exclusively with heating water and plays a crucial role linking heat generation and heat consumption. Its main purpose is to manage these two aspects by balancing out differences between the energy being generated and the energy being consumed so that the entire heating system runs in an economical and ecological way. In this context, a key aspect is the intermediate buffer storage of surplus heat, such as that obtained via a solar plant during the day and discharged when it is needed. In this way, the buffer storage tank decouples the generation of heat from its consumption in terms of time and in terms of hydraulics.
The buffer storage tank offers numerous benefits, such as the fact that the heating does not need to react to every small demand, and the heat from cost-effective, renewable sources can be used more effectively. The EnerVal programme from Hoval comprises a wide variety of models in different sizes, allowing various technical requirements to be met. That means the right EnerVal buffer storage tank with the right volume can be found for virtually any heating system.

Protect your investment with the Hoval maintenance and service packages.

Hoval offers customised maintenance agreements that are tailored to your specific safety needs. These service packages allow you to protect your investment and benefit from a safe, reliable heating system. The Hoval experts carry out inspections and optimisations on your system on a regular basis to ensure that it is running smoothly. As well as saving energy and money, a well-maintained system will also prevent time-consuming faults. In addition, your system’s service life will be extended – making a clear contribution to sustainability.