It is estimated that 35% of treated water is lost to leaking pipes and that 95% of the leaks are in the small diameter service pipes connecting the distribution pipes to the users’ water meters. The service pipe leaks, unlike distribution pipe leaks, are difficult to detect because they are before the meter and water loss is relatively low. Thus water pipe leaks can go undetected for years
On a global scale, it is estimated that 35% of all treated water is lost due to leaking pipes, however in some countries it is as high as 60%. This has a major economic and environmental implications for countries around the world.
Case studies from various cities have shown that 95% of leaks occur in the small diameter service pipes connecting the distribution pipes to the users’ water meters.
In South Africa, approximately 40% of Johannesburg’s supply is nonrevenue water (NRW), which means that water capacity has to be 67% higher than necessary to meet demand.
The value of this non-revenue water is R1.1 billion per year, of this 73.3% is lost due to pipe leakage.
Currently water pipes are made from, or replaced with, High Density Polyethylene (HDPE), a decision that has implications on longevity, maintenance and repair. The International Stainless Steel Forum (ISSF) says HDPE is an extensively used option for water pipes, however, they are not the best solution as their estimated lifespan can be as low as 20 years. However, based on experience with stainless steel applications, a lifespan of at least 60 years is expected.
This year at the ISSF’s annual meetings, the forum launched an initiative to promote the use of stainless steel water pipes. It presented an analysis of three case studies from around the world, where stainless steel has been used for water pipes, drawing conclusive evidence that stainless steel is the best material of choice when considering environmental and economic considerations.
In the early 1970s, Tokyo started investigating a solution to its dwindling water supply. From 1980 to 2012 it replaced all service pipes with stainless steel pipes, and many of these are intermittent corrugated pipes.
In 1980, water losses stood at 17% and by 2012, this was down to 2%. Seoul and Taipei have followed Tokyo’s example and the rest of the world can learn from Tokyo, Seoul and Taipei and reduce water losses with the use of corrugated stainless steel pipes.
Analysing the data from Tokyo and Taipei, it was discovered that the majority of water loss occurs in service pipes, which connect distribution pipes to the consumer’s meter. In Taipei 95% of water leaks occurred here in the service pipes and 95.7% in Tokyo, where leakage is slow, not visible and undetected by meters.
Leaks in distribution pipes, mains and sub-mains, are quickly detected and repaired due to visible leakage.
Leaks in domestic pipes (i.e. after the water meter) are detected quickly by the consumer.
The reasons for leakage in service pipes was mainly through corrosion in metallic pipes and breakage (thermal stresses and traffic vibration stresses) in plastic pipes. Using corrugated pipes also significantly reduces the number of connections needed, and therefore potential leak sites.
Corrugated stainless steel piping is also easy to install in difficult locations. It can be done on site and manipulated in the ground without any need for excessive elbows and connections, resulting in significantly less leakage.
TOKYO CASE STUDY
Tokyo embarked on it’s replacement of lead water pipes with stainless steel in the 1970s, a project that has taken 32 years.
The government was committed to installing 100% stainless steel piping with a move to corrugated product for all service pipes. It believes stainless
steel is the best decision for reducing leakage rates and improving hygiene of drinking water.
ISSF interview with Tokyo Waterworks
Why did you start to replace the service pipe with stainless steel?
In the 1970s Tokyo’s lead water piping system needed to be replaced. Not only was the system a health hazard, but the city needed to minimise risks to its water supply.
It chose stainless steel for these reasons rather than for economic reasons, but these have ultimately also proved beneficial in the long term.
Stainless steel was chosen as it solved the following issues:
• Securing water resources by preventing water leakages,
• Safety and water quality by removing the threat of lead poisoning, and
• Security, due to the threat of earthquakes.
What were your grade selection criteria?
To ascertain what material would perform best, burial tests were done at 10 different sites. Stainless steel grade 304, grade 316, and copper and steel were buried for 10 years.
Stainless steel performed best due to its corrosion resistance. Some pitting was evident on 304 at the harsh marine environment at Okinawa. No pitting corrosion occurred on 316.
Were there any unexpected problems with stainless steel?
There were problems with some bronze stop-cocks and these were replaced with stainless steel stop-cocks.
What are the benefits of using stainless steel?
The project has been a success. There has been a reduction in the leakage rate, a significant cost savings and an improvement in water quality. The system is also earthquake resistant. The city considers the reduction of leakage and effective use of water resources as the greatest benefit.
SEOUL CASE STUDY
Seoul’s replacement of pipes started in 1984 and the project is still on going. To date, 95.6% of the 13 668 km long pipeline has been replaced, with a budget of $2.8 billion. Stainless steel was chosen due to the success seen in the Tokyo project.
An ISSF interview Seoul Waterworks
Why did you replace the service pipes with stainless steel?
The decision was twofold. Seoul needed to improve drinking water quality by solving the corrosion problem as well as reduce leakage through water pipes using high strength materials.
What were your grade selection criteria?
Stainless steel grade 304 was chosen as the most cost effective option.
Why use corrugated stainless steel pipe?
Corrugated stainless steel is a game changer as it reduces leakage in joints and fittings. It is easier to bend on site and has fewer maintenance and repair problems. The very successful case study in Tokyo proved it is the perfect solution.
Have there been any unexpected problems with stainless steel?
There have been incidents of soil and stray current corrosion. There are still some leakage issues at joints installed before 2005.
What are the benefits of using stainless steel?
The use of corrugated stainless steel water pipes has reduced leakage and improved water quality. Before the initiation of the project there were 10 water treatment plants in Seoul, treating 7.3 million m3 per day. After its implementation, this dropped to six water treatment plants, treating 4.5 million m3 per day.
Why didn’t you consider plastic pipes?
Plastic pipes are prone to cracking due to shock and break when there is thermal stress.
Seoul’s temperature varies from 35o in summer to -10o in winter and plastic pipes cannot handle these temperature variations without cracking.
What are the benefits of using stainless steel?
There has been a reduction in leakage and an improvement in water quality.
TAIPEI CASE STUDY
After a 2002 drought left reservoirs drained and part of Taipei without water, the city embarked on a project to replace its existing plastic water pipes with stainless steel. A move that resulted in Taipei surviving its 2014 drought with no disruption to water supplies.
In 2002, water revenue rates were less than 50% in certain areas of Taipei, with 80% of leakages occurring in plastic pipes. The move to stainless steel has proven extremely successful, with replacement continuing.
CONCLUSION
Corrugated stainless steel water pipes have changed the playing fields. They are a cost-effective alternative to copper and plastic plumbing systems and have been proven to be more effective over the long term. They provide easy installation, ensure better taste and water quality, reduce leakage by at least 50% and can withstand temperature and seismic changes.