Water Corporation uses a range of different types of pipes in its water supply network
Pipes are an integral part of Water Corporation’s operational assets. It manages over 34 000 kilometres of pipes that supply 992 170 properties in six regions across the state (Figure 1). Of the 992 170 properties supplied across the state, 80 per cent are in the metropolitan area and 20 per cent in country regions. These pipes and associated assets have a value of $11.72 billion.
- trunk mains – generally larger than 500 millimetres in diameter and carry high water flows and transport water from the source to large storages or other sources
- distribution mains – generally larger than 250 millimetres in diameter in the metropolitan area but may be smaller in country regions and carry water from storages to reticulation pipes
- water reticulation pipes – smaller than trunk or distribution mains and carry water to customers
- farmlands reticulation pipes – these are similar to water reticulation pipes and carry water to farmland services.
Trunk and distribution mains are generally located above ground in country regions and below ground in the metropolitan area. Reticulation pipes are located below ground and account for over half of all pipes. The pipes in the water supply network are made from a range of different construction materials. The key types are asbestos cement which account for 31 per cent of all mains and pipes, polyvinyl chloride at 24 per cent, steel at 17 per cent, cast iron at nine per cent and reinforced concrete at seven per cent.
The standard economic life of pipes varies from 30 to 110 years depending on their construction material and size. For reticulation pipes, the standard economic life ranges from 80 to 110 years. Less than one per cent of pipes have a standard economic life as short as 30 years. The replacement value of the pipe network is $11.7 billion (Table 1).
Overall, pipes have performed well but the frequency of bursts and leaks is considerably higher in country regions
The Water Corporation have generally performed well against its previous licence target for leaks and bursts. Since 2010, the average statewide rate of leaks and bursts has been just under 18 per 100 kilometres per year (Figure 2).
Leaks and bursts are an important indicator of the condition and performance of pipes. The Water Corporation’s previous licence included a performance standard to maintain the statewide leak and burst rate below 20 per 100 kilometres of pipe. This standard was not included in the current licence which came into effect in November 2013 following the commencement of the Water Services Act 2012.
Although the Water Corporation has recently experienced a number of high profile
pipe bursts in the metropolitan area, its rate of leaks and bursts has been the lowest amongst the 10 water utilities across Australia that serviced more than 100 000 connected
properties in 2011-12. The highest rate among similar sized utilities
was 40 per 100 kilometres in 2011-12.
In the metropolitan area leaks and bursts have been well below the overall average statewide performance (Figure 3).
In country regions leaks and bursts have been considerably higher than the metropolitan area. Since 2010, the average annual rate of leaks and bursts in country regions was 21 per 100 kilometres of pipe compared with fewer than 13 in the metropolitan area. At June 2013, the rate in country regions was above 20 leaks and bursts per 100 kilometres. They were also above the previous licence standard between March 2010 and September 2011 (Figure 4).
The Goldfields and Agricultural region, with its extensive farmlands pipe network, is a major contributor to the higher levels of leaks and bursts in country regions. The Water Corporation has agreed levels of service with its customers in country regions that reflect the lower consequence of failures, while at the same time conducting some refurbishment and replacement works to improve performance in the region.
The number of leaks and bursts across the state is predicted to continue below 20 per 100 kilometres of water pipe until at least 2033. However, in 2033 it is predicted that the rate of leaks and bursts in country regions will be over 22, compared with 14 in the metropolitan area.