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Heating ABC


In common parlance, the boiler is known as an electric water heater. It is often only used to prepare domestic water and has a volume (depending on the size of the household) of up to 200L.

Service water

In heating technology, service water is used to describe the drinking water that is used in the kitchen and bathroom. It comes as hot water from the tap and shower and has drinking water quality.


The hot water consumption when showering depends largely on which shower head is used. Conventional shower heads use between 12 and 15 liters per minute. An energy-saving shower head, on the other hand, can provide the same level of comfort when showering at around 6 to 7 liters per minute.

Instantaneous water heater

Instantaneous water heaters heat the water as it flows through the device. This requires rapid and large energy transfer, which is why instantaneous water heaters often use 12kW or more. The use of instantaneous water heaters is always worthwhile when warm water is rarely needed.


Gas is the energy source that has experienced the largest price increase in recent months. It can be assumed that gas will no longer become cheaper in the future due to rising CO2 prices. Gas as an energy source has a poor environmental balance. Depending on the age and efficiency of the heating system, it may be worth considering switching to more sustainable energy sources. There are advisory centers that can help you make the right ecological decisions.

From a financial perspective, such a change can also prove to be quite sensible, especially when viewed from a long-term perspective.

Heating water

In heating technology, heating water is the water that circulates in the heating system and transports thermal energy. The heating system is a closed circuit between the boiler and radiators.

Chimney effect

The chimney effect is based on heat flow: warm water above a radiator rises and accumulates (until it is tapped) at the top of the storage tank. This creates a movement of the water in the tank, which is compensated by a flow of cold water from the lower storage area to the heating element.

Lime (calcification)

Minerals are dissolved in tap water. The amount of dissolved minerals in water is measured with the so-called hardness level. What makes sense for nutrition can interfere with hot water preparation - the minerals are deposited on surfaces when heated and can lead to calcification of the heating element. Depending on the local hardness level, it is recommended to clean the heating element with, for example, citric acid.


Legionella are bacteria that like to form in still, warm water. Inhaling water vapor contaminated with Legionella can cause a lung disease, also called “Legionnaires’ disease.” Therefore, there are strict rules in the European standards to prevent legionella infestation.

Legionella forms at temperatures between 25°C and 50°C. At 55°C they die, above 65°C within a few minutes.


According to the German Drinking Water Ordinance, hot water tanks with a volume of 400L or more must be checked for legionella at least once a year.

Even with storage units with smaller volumes, it is recommended to ensure that the storage unit reaches at least 60°C at least once a week.


After a long period of standstill, it's not a bad idea to flush the water pipes - for example after a long holiday.

sacrificial anode

A sacrificial anode is installed in enamelled tanks. The sacrificial anode ensures that the material of the hot water tank does not corrode (rust). The sacrificial anode is made of magnesium, which has a higher electrochemical activity and therefore reacts (is attacked) before the steel of the storage device. Sacrificial anodes should be replaced regularly. The service life of the hot water tank is significantly extended by using a sacrificial anode.

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