Water distribution system
The water distribution system of the Brno supply network is highly diverse both in terms of profiles, age, technical condition, failure rate and the use of pipe materials. The total length of the water supply mains, including the conduits, is approx. 1,280 kilometers connecting approx. 46,850 pieces of house connections. Prevailing part of the water network is made of metal pipe materials, i.e. 780 km, is made of gray cast iron, 220 kilometers is made of ductile cast iron, 130 km is made of steel pipes and 86.5 km is made of plastic materials (PE and PVC). The rest consists of glass-fibre reinforced plastic pipes (the Vír conduit), asbestos-cement etc. The newly used pipes made of ductile cast iron are supplied with internal cement or polyurethane lining and external corrosion protection guaranteeing their long durability and preventing from incrustation inside the piping. The remaining length of the network is made of other pipe materials, i.e. eternit pipes, PE pipes, glass-fibre reinforced plastic pipes and, in exceptional cases, PVC pipes.
An overwhelming number of the pipes are laid in the ground in a classic way. In the new residential areas of Vinohrady and Kamenný vrch the pipelines are laid in walk-through, excavated combined service networks - underground (secondary) collectors. The construction of the secondary collectors in the central part of the city continues by tunnelling. A part was completed previously, including laying of pipelines, the remaining part (e.g. Kobližná St., Nám. Svobody) is being equipped with services and will be finalized before the end of this year. Thus, the permanent digging in the streets in the city centre caused by repair of bursts on the system, not only on the burst-prone pipelines, will disappear.
The secondary collectors in the city centre are related to the primary collectors tunneled since 1974 in a depth sometimes exceeding 25 meters below the ground. Besides other services, the primary collectors house water supply mains of profiles of DN 300 - 600 in a length of approx. 6.9 kilometers.
Between 1960‘s and 1980’s, extensive development of the water supply system, construction of new water-related structures, extension of the water supply system in new residential areas and extension of the water supply system to the suburbs were in the forefront of interest. The renewal of those parts of the water systems that were approaching the end of the service life, was only performed in a minimum extent, usually following emergency situations. Unfortunately, the quality of work was underestimated even during the new construction and poor quality pipe materials and fittings supplied by monopoly suppliers from the former countries joined under the Council of Mutual Economic Assistance were often used. This situation is now reflected in a high demand for the network renewal, repair of bursts and defects on the system, replacement of malfunctioning and burst-prone fittings etc. The age of approximately 280 kilometers of water mains is past 50 years and even pipes laid before the year 1900 that are more than 100 years old are still kept in operation. A high number of bursts on the network and fittings keeps being repaired. The quality of the pipe materials of pipes laid in the collectors was also underestimated. The steel pipes corrode fast, it is necessary to provide frequent and costly re-coating of the pipes and some of the mains had to be replaced by non-corrodible fibreglass pipes due to corrosion and the burst rate. The overall condition of the water supply system is also caused by the quality of conveyed water. The water treatment plants were overloaded, the treatment technology could not cope with the deteriorating quality of raw water, it was not possible to ensure an adequate pH value, ferric flocs were formed even in the pipes, which resulted in intensive growth of incrusting solids n the pipes and pipe corrosion.
The changes resulting in new social-economic conditions have started bearing fruit also in the field of repair, maintenance, renewal and construction of water supply systems:
- reduced water consumption and substantial improvement of the quality of water supplied to the consumers have minimised the negative impact of water on the metal pipelines
- access to new, high quality pipe materials, valves, repair materials improves the quality of performed work and thus the reliability of the water system operation
- although the present progress of renewing the water supply system still lags behind the actual needs, the network has been renewed in a number of places that were in a state of disrepair
- progressive improving of the quality of the water supply systems and execution of a number of measures (e.g. network measurement system) have resulted in reduction in water losses compared to the year 1989 to less than half.
- improvement equipment for repair of the water system, new organisation of work and faster working methods employing new repair materials have accelerated repair of emergency bursts and shortened the water supply disconnection periods
The operation and administration of the water supply system including minor maintenance work is ensured by the water supply system operational staff. The area serviced by the Brno water supply system is divided into 6 districts for the purpose of the system administration with allocated district technicians and district fitters provided with breakdown vans. Special surveys are performed by a crew from the diagnostics department, the task of which is to detect hidden bursts on the water supply system and to identify and specify the location of hidden bursts using efficient electronic devices and correlators, to survey pipes and fittings, to evaluate flow rates and pressures in the district measuring spots in the established network measurement system, to identify and localise water leakage detected by the measurement, to measure flow rates using a portable ultrasound flow meter etc. Corrosion protection of the water supply system and active corrosion protection systems are taken case or by a corrosion technician, who is also in charge of checking of water pipelines in the collectors and maintaining of electric-controlled valves on the water pipelines located in the collectors.
Repair of bursts and defects on the water supply system is ensured by the repair and maintenance department seated in the premises at Rybníček 12. A total of ten 2-member or 3-member crews are available for the repair work and they are equipped with a breakdown van with a stand-by generator, pick hammers and other standard small tools. If allowed by the buried lines, earth work is performed by heavy-duty mechanisms, such as diggers, trucks, cranes and other special mechanisms, provided by the transport department as required by the water system department. Earth work following selected bursts and defects on the water supply system are also ordered from specialised construction companies. Likewise, most of the road reinstatement work in the places of the excavations is provided by suppliers.
Flexible emergency water supplies to inhabitants during water supply disconnections are taken for granted.