Hot water tanks from the point of view of temperature and energy confrontation

The main cause of outbreaks of Legionnaires' disease is from contaminated water sources. About 3 in 10 cases of Legionnaires' disease are due to poorly maintained water storage in buildings. A Tankless water heater can reduce your water-heating bill by five percent to fifty percent or more. A Tankless water heater is a continuous flow of hot water because it instantly heats the water as it goes through the heater. The question is if the Tankless water heater is more efficient than the tank water heater? In our experiment, using Water Quality Management methods, the water heater tank was verified as a source of ubiquitous bacteria’s that can cause health problems to users. Are the solar hot water systems also dangerous? The use of solar energy is very prospective and in the future it will be used in various sectors. The subject of the paper is a simulation of the operational modes of hot water preparation focused on its temperature and energy impact