Water supply network
The distribution of water and drinking water is usually carried out in a water distribution system permanently installed. This includes facilities for storage, pressure increase, distribution, quantity measurement and sampling. Measures for water purification may be required prior to feeding to the water distribution system. A distribution system must be such that the amount required is of the required quality and the correct pressure.
In Germany, the demands on the distribution system by the DVGW worksheets are defined eV for the distribution of drinking water.
In general, the municipal drinking water demand is calculated taking into account the fire case, since the public drinking water system serves most of the central fire water supply of cities or towns.
According to § 17 paragraph 2 of the Regulation, the drinking water supplies for drinking water and rain water must be permanently marked with different colors in Germany. Rainwater harvesting systems may not be directly connected to the house wiring.
Elements of the water distribution
For the storage of water in distribution systems, various forms of water storage can be used, which may differ in terms of their location in the network and its design differ from each other.
Pumping stations and booster stations
Pumping stations are used for water pumping. These can be used either in the network, promote vessel or the pressure increase. As pumps usually come centrifugal pumps. Piston pumps are historically today. Centrifugal pumps can be operated at a constant speed or variable speed. Larger pump stations usually have several pumps which can be arranged in two forms:
- Pumps connected in parallel to increase the flow rate,
- Pumps connected in series to increase the pressure and thus the head.
To control the pumps, the following methods are used:
- Two-point control according to the water level in a high container,
- Rules taking into account the pressure in the supply system (on / off of the pump, changing the rotational speed ).
To avoid pressure surges in the pipe network either air chamber (closed container in which pressure pulses are buffered by a volume of air ) or appropriate approach strategies of variable speed pumps are required. If the supply pressure of the network is not sufficient on site, can and in the buildings by appropriate pressure boosting systems (DEA ) of the pressure required to supply all bullets are created.
As line materials come in drinking water cast iron, steel and various plastics such as polyethylene, usually HDPE, high density polyethylene or polyvinyl chloride used. Lead pipes are no longer used since 1973 and have been almost completely removed from the nets. In a few cases, even service lines are present as lead pipes, but they must be replaced by 2013 to comply with the valid from December 1, 2013 Limit value for lead of the drinking water regulations. Asbestos cement pipes expands every day under strict conditions again because of the high risk of lung cancer from asbestos fibers, which are absorbed through the respiratory exists. According to studies by the WHO, there is generally no health risk from exposure to asbestos fibers in drinking water, because asbestos fibers pose a health risk only when recording via the respiratory tract. A recording of asbestos fibers from drinking water over the air requires very high concentrations of asbestos fibers in water, which, at least in German drinking water are unlikely according to investigations by the DVGW.
For drinking water should be in the municipal area of the pressure in the focus of a pressure zone 6 bar. At the same time, a minimum pressure of 1 bar should be given to the least favorable sampling point in the distribution network. In general, the highest static pressure at 8 bar and the highest system pressure at 10 bar, the difference of 2 bar serves as protection against pressure surges. Certain minimum pressures at the transfer point are for building, depending on the number of storeys, prescribed to the consumer. These requirements are different for new-build and existing networks. Usually, the pressure should be 2 bar (EC ) amount to 0.5 bar per floor. Thus must be provided for higher buildings where appropriate, domestic pressure boosting systems. Distribution systems without direct consumer may be connected bar with pressure values above 10, but should again be reduced accordingly in the water delivery to the customers the pressure.
The flow rate should be chosen such that on the one hand, the pressure losses remain low (low speed) and on the other hand, the residence time is not too large ( bacterial regrowth, increase in temperature, palatability). The rules of the DVGW sets the benchmark for an average hourly flow rate of greater than or equal to 0.005 m / s ( 432 m / d).
The pipes can be connected to either weld or fittings to pipes. For laying open ditches ( Künetten ), tunnels, or underground pipe jacking can be used in the ground by pressing or flushing. Underground pipelines are properly beds in sand to prevent damage.
The water transport may also take place in channels with free water surface ( open channel ). If necessary, aqueducts are required. However, large water transmission pipelines by gravity sewers are also culverts, which are pressurized pipes for crossing valleys, adds.
Fittings and water measuring devices
In the course of the line network gate valves, check valves, backflow preventer, pressure limiter, discharge devices, fire hydrants, sampling valves, pressure gauges and house connections with water and water meter house lead to necessity are required.
There are two basic network types: Verästelungsnetze and mesh networks.
Verästelungsnetze are distribution networks, which have a tree-like structure. This web form has the advantage of clear flow conditions and a lower Bauaufwands as mesh networks. The disadvantage is the high susceptibility of the system, because if an interruption of all downstream power supplies can no longer be supplied. Transmission grids and local power supplies in marginal areas are often designed as Verästelungsnetz. Other examples are the cold water distribution systems in a residential installation.
Meshed networks consist of interconnected single strands. It is advantageous to the high security of supply in case of malfunction and at peak times such as the extinguishing water withdrawal. The disadvantages of this network configuration are in contrast to Verästelungsnetzen higher construction costs and more ambiguous flow conditions. This web form is used for most local area networks. A special form are loop networks; in these attempts in the comprehensive the distribution network loops to produce a unique flow direction. For this example, a local area comprehensive transportation lines or rare fixtures such as check valves are used.