Effect of pressure on burst and leakage in drinking water network

Water distribution systems and failure to prevent the formation of burst are studied. Bursts occur in distribution systems because of poor workmanship and material defects, traffic load, rupture from earthquake, soil corrosion and high pressure. Planning stage creates negative effects due to pressure. To eliminate pressure on the network, average of 30 to 60 and 20 to 80 mws should be applied critically. However, in some cases the provision of these terms is very difficult. Slope more than that cannot be done in cases of separation. There should be need to think of different options. In such cases, the pressure within the network itself as part of high pressure in the left districts reduced pressure through a valve to bring the appropriate pressure. City of Adapazari network in accordance with the regulations of Province Bank is divided into two floors: high regions of city where Maltepe and Hizirtepe districts get water from the tower tank. Hizirtepe malfunctioning occurred due to complaints from high pressure gradient. As a result of increased water loss, the complaints of subscribers and business costs are increasing. A specific point of pressure measurement made at the highest pressure to be right enough pressure has been reduced. After implementation, there has been a huge drop in the number of bursts. The idea of water tower supplying water to the region by using two pumps is promoted. Before and after application, pump runtime is compared. Daily average working time of two pumps for the water given to the distribution system decreases from 26 to 22 h, despite increase in temperature and seasonal decline.


INTRODUCTION
Reduction of water loss has accelerated at the turn of the century (Morais and Almeid, 2007;Marunga et al., 2006;IWA, 2000;Lambert, 2000).Water companies are making major investments to reduce leakage through traditional solutions and evaluation and application of new technology (Ulanicki et al., 2000).
More efficient use of resources in operation and management of water distribution system has gained importance by decreasing of water sources.With increasing water quality, uninterrupted water supply and customer satisfaction are gaining more importance.Burst in drinking water distribution systems causes dissatisfaction for subscriber because of water losses and interruption.Nowadays, uninterrupted water supply is a quality of service indicator for water administrations.
Great progress has been made in developing innovative methods to determine the effects of the pressure on the losses incur due to defects and leaks within the potable water supply system (IWA, 2000).In the studies conducted in England and Japan, it was determined that pressure is one of the main reasons for defects and leaks in the system.
The domestic water systems are designed in such a way that they provide sufficient pressure for the system even during daytime when water consumption is at its peak.Load losses increase due to friction, and the input pressure decreases.As a result of the design, during the times when higher pressure is not necessary, the system will be subject to excess pressure.Thus, it is the later hours during night time and very early in the morning when the pressure is highest that breakdowns occur (Mckenzie and Wegelin, 2005).In many countries, the institutions responsible for the management of water system have begun to manage the sustainability of the substructure through the pressure method, diminish the breakdowns and prevent the loss of water due to such breakdowns.Diminishing the number of breakdowns and loss of water through pressure method can be defined as diminishing the excess pressure level which may cause leaks and breakdowns for consumers to more reasonable levels.This prevents them to incur any problems through the management of system pressure.
Diminishing the excess level of pressure in the distribution system causes lesser breakdowns to occur.The benefits assumed to be obtained by diminishing of the pressure are listed as follows.

Diminishing the costs due to breakdowns and repairs
Decreasing the number of breakdowns is the same as diminishing the number of leaks.This would extend the life of the distribution system and decrease the operating costs.
If a renewal criterion may be determined by assuming "X" number of breakdowns on "Y" kilometers of pipes in "Z" number of years, the amount of investments saved for renewal will be diminished.
The frequency of defects that occurs in the system relates to how well the breakdowns are managed.Renewing the system on which breakdowns occur frequently is not the primary or the sole option for diminishing the repair costs and breakdowns (Thornton and Lambert, 2005).
The domestic water systems are designed in such a way to ensure efficient operation and to prevent leaks and breakdowns with integrity of all its connecting and supplementary parts.However, this cannot be obtained at all times during applications; even a recently installed pipe may not have homogeneous structure.A certain section of the pipe may not have a uniform thickness.If the sleeve surrounding section is not properly installed, it will be weak against the traffic load, corrosion and other impacts.As the pipe is subjected to pressure in such cases, tearing and cracks may occur.Even if the breakdowns within the distribution system due to pressure occur for a short period of time, they may cause failures.One of the primary actions to be taken is controlling the pressure fluctuations by random measurements (Morrison and Tooms, 2007)

MATERIALS AND METHODS
The water source of the city centre in the Province of Adapazari is Lake Sapanca.The amount of raw water supplied from Lake Sapanca is elevated to the water reservoir at Esentepe Region by means of motor pumps.It is transferred from here to Maltepe Domestic Water Treatment Facility through the water supply lines.The treated water is transferred to the system through the supply lines from the reservoirs at the elevation of 104 m.The elevation of the city centre is approximately 30 m.However, since the upper sections of Maltepe and Hizirtepe Boroughs where the treatment facility and reservoirs are located at the same elevation as the reservoir, the water can be provided by tower reservoir.The water is supplied from the main reservoir to the other reservoir by means of two electro motor pumps with Q = 30.50l/s (flow rate), Hm = 62 mSS (pressure height), Nm = 50 kW (power).Adapazari water supply system was manufactured from HDPE (high density polyethylene pipes).The system was completely renewed following Golcuk Earthquake on August 17, 1999.The distribution systems in Maltepe and Hizirtepe boroughs can be operated separately from either the distribution system and from each other.In order to analyze the effects of pressure on loss of water due to breakdowns and leaks, Hizirtepe was selected as the field of application where it can be controlled by diminishing.The length of the system in the area of application and the diameters are shown in Table 1 and the satellite photos are shown in Figure 1.
The customer at the top storey of the tallest building in the region was assumed to be the critical point and the pressure at this point was measured and recorded.Taking the critical point as the reference point in the way as to not cause them any dissatisfaction in the quality of service, the pressure was diminished through the use of pressure breaker valve.The pressure relating to the subscriber was measured again after the application and it was recorded.In order to verify whether the pressure change had any adverse affects on the subscribers, momentarily measurements of the pressure were made at several points of the system.
The number of occurrence of breakdowns before the application was compared to the number of the same after the application.The water supplied to the system was calculated based on the operating durations of the motor pumps.The operating periods before and after the application were compared (WHO, 2001).

RESULTS
The maximum altitude of Hizirtepe field of application is 80 m. and the minimum altitude is 56 m.The altitude of the reservoir which supplies water to the system is 104 m, and the elevation of the tower is 35 m.As the Piezometer line is taken into consideration the pressure at the part of the system with the lowest altitude is approximately 83 m (around 8 bars).It was seen that the pressure may reach these levels during momentary measurements.The pressure of the system at the highest altitudes is approximately 56 to 59 m.The pressure measured at the top floor of the building which is determined as the critical point is maximum 46 m, and minimum 40 m (Figure 2).
The pressure breaker valve installed to the system was adjusted in the way to diminish the pressure by 20 m.Following the adjustment, the pressure was recorded again at the same point.It was seen that the pressure occurred at an average of 18 m, and at the maximum value of 23 m.Momentarily measurements were obtained from the region and it was seen that no complaints were made (Figure 3).
Before and after the application, the number of breakdowns in the area and the duration of pump operating hours have diminished.The breakdowns occurred based on the months.Since the works to diminish and control the pressure started from February 2009, the number of breakdowns can be seen in the graphic in Figure 4. Significant decrease in the number of breakdowns can be seen as it is compared to the previous months and especially as it is compared to the same period of the year.As the periods include the same section of the years 2008 and 2009, it is determined that the main pipe breakdowns are decreased by 65% and subscriber pipe breakdowns are decreased by 35%.The unit costs of the breakdowns that occurred based on their kinds can be seen in Tables 2 and 3.If the calculations are made based on unit costs, it is seen that the costs diminished by 66% at the main pipe and 37% at the customer's pipe.Also the subscriber's satisfaction increased due to the quality and duration of repair services rendered by the workmen and also loss of water is prevented indirectly.
Due to the durations of operation for the two pumps which supply water to the system by controlling the pressure, it was seen that they started operating less.But, whenever a new breakdown occurred, the durations of operation increased.Prior to the application, the motor Time (s)  Commission of Sakarya University.

Figure 1 .
Figure 1.Satellite Photo of application area.

Figure 2 .
Figure 2. The pressure measured at the critical point prior to the application.

Figure 3 .Figure 5 .
Figure 3.The pressure measured at the critical point following application.

Table 1 .
The lengths of the system in the field of application based on the diameters.