In the hot water system, the distances from production to user should be minimized and well insulated. Water temperature in general should be 55 - 60° C. Under 55° C increases bacterial dangers (Legionnaires’ disease). Over 60° C increases calcium deposition. For hygienic reasons, hot water needs to be heated to 60° C once a month.

Central hot water supply

• During the heating period, hot water is usually provided by the heating system. 
• Although heating is not used in the summer, hot water is still needed. 
• Capacity utilization of the heating system in the summer is very low. Utilization falls below 40% for older systems. (Example: Six of ten liters of oil remain unused.) 
• This costs money and damages the environment. 
• Thus it makes energy sense to prepare hot water in warmer months separately from the heating system– ideally with a solar system or heat pump (see Water heating below). 
• Modern low-temperature furnaces achieve utilization of up to 80% even in the summer (furnace switches off when not needed to reduce losses). Ensure that your buffer is the right size. Rule of thumb: 50 liters of hot water storage per person at 50° C.