Own water supply system
In the case of properties that are not connected to the public water supply , private water supply systems , also called domestic waterworks , are used to supply the residents or users with service or drinking water.
Technical equipment
In a private water supply system, water is pumped from a reservoir into a pipe network. This reservoir can be a well, a body of water or a source in the context of water extraction , in the case of service water systems it can also be a cistern for collecting used water or rainwater.
Single or multi-stage centrifugal pumps are used as pumps for conveying, depending on the pressure requirements . Underfloor or submersible pumps are mostly used because they are characterized by lower operating costs, higher efficiency and lower noise pollution. They are protected against dry running by electrodes hung in the reservoir, which control the water level and switch off the pump when the water level is too low. The pumps are equipped with a backflow preventer so that no water flows back from the pressure line into the reservoir when the pump is switched off . Floor pumps are usually cheaper to buy, but their high maintenance costs increase the operating costs so much that they are not as profitable as floor pumps or submersible pumps. Furthermore, they can only be used with a delivery depth of a maximum of 7 meters, as otherwise the maximum achievable suction height will be exceeded.
An essential component of large and many small private water supply systems is a pressure vessel, usually in the form of a hydrophore or also as a membrane pressure vessel . There is a gas (air or nitrogen ) in the pressurized water tank . The incoming water compresses the gas up to a preset maximum value (e.g. 4 bar). When this value is reached, the pump is switched off. If water is withdrawn from a tap, the gas expands until a certain minimum pressure is reached (e.g. 2 bar). Then the pump resumes operation. The switching tasks are carried out by a pressure monitor which switches the pump on when the pressure falls below the minimum and switches it off when the maximum pressure is reached. This protects the system from pressure surges and the pump from frequent start-up requests.
Small systems do not necessarily have to be equipped with a pressure vessel. They can also be operated with just one pressure and flow monitor.
Regardless of the size of the system, pressure gauges are often installed to monitor the pressure.
A safety valve is prescribed for systems if the delivery pressure exceeds the permissible operating pressure of the pressure vessel by more than 10%.
Legal norms and technical guidelines
Self- supply systems that serve to supply drinking water must meet the requirements of the Drinking Water Ordinance in Germany and must be monitored and sampled in accordance with its requirements.
The corresponding DIN standards and regulations apply to domestic water installations. A distinction is made between large and small systems, with the limit being drawn at 10 m³ / h delivery volume. An EVA must be set up dry and cool, but frost-proof. The safety regulations for pressure lines must be observed. After completion, the self-supply system must be checked by an expert if the following points are not met:
- The pressure vessel is type-tested as standard.
- The air cushion in the pressure vessel is only supplemented by the water pump and not by a compressed air cylinder or a compressor.
- The system conveys such a small volume at such a low pressure that the mathematical product of the two quantities does not exceed 6000 l * bar.