Undetected leakage from pipes accounts for most of the recoverable water loss from the water supply network
Water loss in the supply system affects the sustainability of supply, reduces revenue, and can undermine broader water saving initiatives. While it cannot be completely eliminated, current loss is around 10.5 billion litres above the 19 billion litres a year that Water Corporation estimates is the lowest achievable level of loss. Of the 10.5 billion litres considered recoverable, about seven to eight billion litres was undetected leakage from pipes.
In 2012-13, the Water Corporation supplied over 357 billion litres of water, of which almost 314 billion litres was metered consumption. The difference of over 43 billion litres, or 12 per cent of total water supplied, included over 13 billion litres that was used but not metered or billed for, and almost 30 billion litres (eight per cent of total supply) that was physically lost.
Western Australia experiences some of the highest water loss compared to similar sized water utilities in other states. In 2011-12, Western Australia lost about 90 litres of water per service connection per day. This is compared with water loss in the other similar sized water utilities that ranged from 50 to 96 litres per service connection per day.
Metering errors or customer meter inaccuracies accounted for just over 11 billion litres of the over 13 billion litres of water that was used but was not metered. Unbilled but authorised consumption (for example for firefighting use) accounted for almost 1.8 billion litres and unauthorised consumption (for instance theft) accounted for almost 360 million litres.
Well maintained and managed supply systems will experience some level of water loss, but it can be minimised. The Water Corporation has used an internationally accepted industry standard to estimate that the lowest volume of real loss it could achieve, given its current network, is just over 19 billion litres a year. Current performance at a loss of almost 30 billion litres is around 10.5 billion litres above that benchmark.
The Water Corporation considers the 10.5 billion litres of water to be recoverable. About seven to eight billion litres of it was undetected leakage from pipes. Most of the leakage is from reticulation pipes in the metropolitan area. Less than one billion litres is from trunk and distribution mains.
Water Corporation has a leak detection program in place to reduce leakage from pipes
The Water Corporation has a targeted program to find and repair undetected leakage from pipes. Between 2010-11 and 2012-13, this program covered 7 400 kilometres of pipe (5 550 kilometres in the metropolitan area and 1 850 kilometres in country regions), made 1 286 repairs and prevented 3 430 million litres of leakage. But water loss from undetected leakage is not considered an indicator of performance and information from the leak detection program is not considered when assessing performance for its pipe replacement planning.
Locating where leakage is occurring from pipes across the entire water supply system can be difficult. Leakage from pipes can often go undetected for a long period of time for a range of reasons. The depth of the leak, sandy soil conditions, poorly compacted ground, proximity to sub-soil and stormwater drainage, density of lawns or pavements and the rate of leakage can all contribute to how visible leaks can be.
Undetected leaks can contribute to large volumes of water loss over time. For example, a large reported burst pipe with a water flow rate of 300 litres per minute would lose 108 000 litres if repaired after six hours. Small unreported leaks can also cause significant loss because they can be harder to detect and so go unrepaired for longer. An unreported leak with a water flow rate of five litres per minute would lose 2.6 million litres over a year if undetected.
The Water Corporation’s primary initiative to manage leakage from pipes is its leak detection program. It has run for three years and uses specialist personnel with electronic and acoustic equipment to detect leakage from reticulation pipes. The specialist personnel report information back through Water Corporation’s document management system, and where relevant, repairs are made.
Geology and the type of pipe construction materials are used to target areas for detecting leaks. Locations are prioritised where detection will either find the greatest rate of leakage or where reduction in leakage will prevent or reduce the need to establish more water sources. In combination with other initiatives like district metered areas and water pressure management, it is expected the active leak detection program will result in more leakage being prevented and reduced in the future.
The speed of the repairs made as a result of detection is an area of focus for the program. Currently, repair work is allocated to teams in the field at the end of each area surveyed. But new processes will enable the specialist personnel to issue work orders themselves immediately as they find leaks. Also, each area is surveyed and repaired as part of the program for any issues associated with the quality of repairs and any recurrence of leaks is addressed at this time.
Undetected leakage is not a performance indicator used in pipe replacement planning
Undetected leakage is a key measure of the performance and efficiency of pipes. Pipe replacement is an aspect of managing water loss, along with initiatives such as leak detection, pressure management and the speed and quality of repairs. The leak detection program is gradually providing the Water Corporation with a greater understanding of where and why undetected leakage occurs. Information about the repairs of leaks and bursts found through the program is used in replacement planning, but not the broader information and intelligence about why leakage is occurring. Also, information about undetected leakage is not being used as a performance indicator in planning pipe replacement. Investment in pipe replacement and water loss management initiatives are considered separately within the Water Corporation’s investment planning processes.
The Water Corporation’s investment in pipe replacement is reviewed annually through its Strategic Investment Business Case (SIBC) process. The Water Mains State Wide Renewals SIBC sets out the recent history and current performance of pipes, business imperatives, risk analysis and a range of investment options. Information about reported leaks and bursts is included, but undetected leakage is not considered an indicator of the performance of pipes in the Water Mains State Wide Renewals SIBC. Information from the leak detection program is not considered in assessing performance for its pipe replacement planning.
Although leak detection is an ongoing program, the Water Corporation’s investment in these initiatives is reviewed annually through a separate SIBC. The Water Loss Management SIBC sets out capital investment options for a range of water loss management initiatives and activities. The key investment options include expanding district metered areas, pressure management and smart metering, but there is no linkage to, or consideration of, pipe replacement as an investment option in the Water Loss Management SIBC.