Water-Main Network

the aggregate of pipelines used to supply water to places of consumption; one of the main elements of a water-supply system. Domestic water-supply branches (pipes), through which water is supplied to individual buildings, are connected to the pipelines of the net-work, which are usually laid along streets and highways. Interior networks, which supply water to take-off pipes, are installed inside buildings. In contrast, the central water-main network, which is laid outside buildings, is called the exterior (street or yard) network. Water pipes are used to build a water-main network. The kind of pipe is chosen according to the amount of head required in the network, the nature of the soil, the method of laying the pipes, and economic factors. Cast-iron, asbestos-cement, and steel pipes are most commonly used for underground installations; pipes made of rein-forced concrete and plastic are also used. The depth at which the pipes are laid varies with the depth to which the soil freezes, the temperature of the water being supplied, and the operating conditions of the system. (In the central belt of the USSR, pipes are laid at a depth of about 2.5 m.) The minimum depth is defined by the necessity of protecting the pipes against destruction by dynamic (transport) loads.

Water-main networks are equipped with shutoff devices, such as dampers and valves, to seal off individual parts of the system; and take-off devices, such as fireplugs and sometimes street standpipes, for areas that are not yet completely equipped with house inlets. Hydrants and gate valves are usually installed in special prefabricated reinforced-concrete or brick shafts with removable manhole covers.

Because of technical requirements, the head in water-main networks of residential localities should not exceed 6 atmospheres. Local pumping stations are constructed to supply water to individual multistory buildings.

Water-supply networks should provide a reliable and continuous supply of water to the consumers. This condition is met by installing circular networks consisting of adjacent closed loops arranged according to the layout of the city. In case of accident, the damaged portion of a main can be cut off by gate valves without interrupting the supply of water to the other pipelines in the network. In branched (dead-end) net-works, an accident anywhere in the network interrupts the flow of water to all parts of the network lying beyond the damaged portion. Therefore, branched networks can be in-stalled only in cases where interruptions in the water supply can be tolerated. All systems in which the water is to be used for extinguishing fires are generally of the circular type. A distinction is made in a water-main network between the mains, which carry water to the remote parts of the region being supplied, and the distributing network, which supplies water to the individual house branches.

The design of water-main networks, particularly circular networks and those receiving water from several pumping stations, is a very complex and labor-consuming task. The use of computers is the most expedient way to achieve this purpose.