Water Distribution : Old Pipe Network Maintenance Project

Date 2015-06-25 Category Water Supply (Arisu) Updater scaadmin
Seoul Metropolitan Government
Last Update


Systemic Maintenance based on the “Comprehensive Old Pipe Maintenance Plan”
The “Old Pipe Maintenance Plan” was adopted in 1984 to supply clean tap water to household consumers, minimize leak, and build a stable inter-region supply system. Based on the plan, of the 13,728km that run throughout Seoul, 96.1 % of the old water pipes, or 13,192km, were replaced by the end of 2013.
By 2018, all other remaining old water pipes will be replaced with corrosion-resistant cast iron pipe and stainless pipe. The total budget for the replacement was set at 3.5 trillion won, 2.9trillion won of which was invested from 1984 to 2013; another 622 billion won will be injected by 2018.
After 2018 when all the pipes will have been replaced completely, healthy and tasty tap water produced in water purification plants will be distributed to Seoul citizens through the new and clean water pipe network.

Overview of the Policy


It is crucial to supply healthy and safe tap water produced in purification plants to household consumers without any contamination in the distribution process. No matter how healthy and safe the water produced in the purification stage is, outdated, rusty water pipes will pollute the water, damage citizens’ health, and incur massive financial loss due to water leak.
Recognizing the paramount importance of water pipes, the Office of Waterworks of the Seoul Metropolitan Government began maintenance works for old pipes to minimize leaks and ensure the health of our citizens.

Process of Policy Implementation

Need for Pipes Repair and Japanese Colonial Era
In general, the life span of transmission and drainpipes is considered to be 30 years, whereas supply pipes last 20 years. It was in 1908 when the water system was first introduced in Seoul, so the initial transmission and drainpipes would have already come to the end of their life by 1943. Since Imperial Japan was engaged in war around the time, however, it was probably too under-resourced to replacement the old pipes – an assumption confirmed by the book titled History of Japanese Civil Engineering, which records the state of Seoul’s water system until 1940. The book made no mention of any maintenance or repair work of water pipes.

Post-WWII and Economic Development
After Korea‘s independence from Japan, records were found on the construction of drainpipes and supply pipes, but no reference can be claimed for the replacement of old pipes. Records on replacing the old pipes of Seoul’s water system first appeared in the Overview of City Management issued in 1962. According to the document, the “5-Year Plan to Prevent Leak” was set with 1962 as the base year to reduce leak rate of 57 % in 1961 to 35 % in 1966. A total of 265.46 million won was allocated to the project to replace 113 km of drainpipes.
The second plan was implemented for 10 years from 1965 to 1974, with the project costing 1.65512 billion won. The project replaced a total of 418 km, which consisted of 151 km of drainpipes and 267 km of supply pipes, or 62 km longer than the originally planned 356 km.
As of the end of 1971, old transmission and drainpipes accounted for 126 km or around 9.4% of a total of 1,341 km; old supply pipes were 939 km long or about 17.9% of a total of 5,239 km. The third replacement plan was carried out from 1972 to 1981 with 6.179 billion won. A total of 1,262 km were replaced including 324 km of drainpipes and 938 km of supply pipes, accounting for only 39.7 % of the planned 3,179 km.

Stable Growth and Quality Improvement
Replacing old pipes proved to be a very challenging task since the number of old pipes remained sizable despite the consistent replacement. Old drain and supply pipes accumulated annually to reach a total of 1,370 km by the end of 1980, with 186 km of drainpipes over 35 years old and 1,184 km of supply pipes over 20 years old.
Until 1990, no tangible outcomes were seen; only 150-700 km of pipes was replaced annually. It was from 1991 to 1993 when the old pipes were replaced in large numbers.
A total of 4,200 km were replaced for three years -- 1,200 km in 1991 and 1,500 km each in 1992 and 1993, marking a record-high replacement in a short period of time; 500-600 km have been replaced every year since 2000.
From year 2000 onwards, we have been thoroughly inspecting rusty pipes and washing outdated pipes to ensure the quality of pipe networks. In particular, we focused on establishing both net and line for conduit so that tap water can be supplied without water interruptions. In addition, we set up a support team dedicated to improving old indoor water pipes; the team evaluates the state of old pipes and gives financial support to households to facilitate replacement.

Modernizing Water Pipes and Management
Modernizing management became possible thanks to our Geographic Information System (GIS), a system that creates a digital database of design and properties information of water pipes, supporting components, valves, fire hydrant, and water meter, including turning attributes and current data into figures and maps. In addition to GIS, we have conducted aerial surveys, checked underground facilities, streamlined different data, and created a database since the mid- 2000s. Through such multi-layered efforts, we are getting closer to establishing a comprehensive management program that combines GIS and Management Information System (MIS).
We pursue systemic, scientific water-related data management, rational decision-making process on facility investment, scientific facility maintenance, preventive management system for stable water supply, higher efficiency in processing tasks in water facilities, and highest-quality public service.

Introduction of the Policy on Old Pipe

Maintenance Plan
As part of the “Old Pipe Maintenance Plan,” 36.6 billion won was injected for 22 years from 1962 to 1983 to replace 1,821km of old pipes. Note, however, that the highest priority during this period was resolving water interruptions, not ensuring the cleanliness of water.
Today, water interruption is no longer a major problem; even if there are some issues, they are caused by rust leak, old domestic pipes, and narrow gauge. Therefore, to address this issue effectively, we started subsidizing constructions of old interior pipes in the latter half of 2007.
From 1984 when maintenance works on drain and supply pipes began in full swing, we established a comprehensive maintenance plan and invested 2.8777 trillion won to replace 96.5% or 13,192km of the 13,668km old pipes until 2013. The remaining 476km old pipes will be fully replaced by 2018.

A total of 13,791km conduit was extended as of the end of 2013. The length of transmission pipes from purification plants to reservoir is 552km; drainpipes from reservoir or drainage pump to water supply facilities span 9,811km, and supply pipes from reservoir to household consumers, 3,335km. As shown in the table below, the number of extended transmission pipes increased thanks to the construction of new pipes followed by pipe network maintenance, whereas supply pipes decreased in number as a result of continuous maintenance of unused pipes. There were almost no changes in the extension of drainpipes, but old pipes were mostly replaced thanks to the maintenance works on drain and supply pipes.
Steel pipes were mostly used for transmission pipes, whereas pressure- and corrosion-resistant ductile cast iron pipes and PE pipes were utilized for drainpipes with gauge of over 80km. For supply pipes with gauge under 50km, galvanized steel pipes were used before 1987, but stainless steel pipes and copper pipes were utilized from late 1987; stainless steel pipes have been commonly used since 1993. The current status of water pipelines is as follows:

Maintenance of drain and supply pipes of Seoul first began in 1984 when the “Old Pipe Maintenance Plan” was formulated; since then, maintenance efforts continued. The efforts have expanded to include new maintenance targets such as pipes in renewed and rebuilt establishments and coal tar enamel-coated steel pipes among transmission and drainpipes. The project is set to be completed by 2018, and results per stage and future plans are listed in the table below.

Policy Experience & Knowhow

Establishment of the “Drainpipe Network Maintenance Plan”
We first launched a task force team tasked with forming a long-term plan for drainpipe network maintenance. In line with this, we divided Seoul into 39 blocks; in each service area, block programs developed in the US such as KYPIPE Ⅲ and CYBERNET 3.1 were used to perform pipe scan. We carried out comprehensive and close probing of all existing drainpipes, drew maps, and planned a proper drainpipe network for each regional water reservoir.
Phase of Drainpipe Maintenance

Small Block Planning
The entire city of Seoul was divided into 39 blocks of regional reservoirs, which were again categorized into 1st, 2nd, and 3rd reservoirs composed of 2,037 small blocks. Block planning enabled more efficient drainpipe management, facilitating regional maintenance and adjustment of demand for water supply.
Procedure for Small Block Maintenance Planning

Old Pipe Maintenance Plan Aligned with Basic Plans on the Water System
The “Old Pipe Maintenance Plan,” which was implemented in line with the “Basic Plan for Waterworks Improvement,” divided Seoul into 2,037 small blocks. We tried to use the longitudinal excavation method whenever possible in fixing unused pipes. Moreover, when building new drainpipes, we made sure the size is at least 150mm-wide gauge so that, if necessary, we can turn this area into direct water supply. The 150mm width is also suitable for monitoring by Seoul’s maintenance and management system. (At the same time, blocks were clearly separated so that the minimum flow rate could be measured per block.)
Moreover, we required the identity of all builders to be disclosed when they engage in pipe works so that we can ensure responsibility and quality. To this end, we developed an online program called “Real Name System” in which the names of constructors are listed and attached to the connection of the pipeline structure. The system helped us better manage the workers, both electronically and at the site; this in turn contributed to enhancing the responsibility of the workers and the quality of the work they do.
Meanwhile, a central management system for construction materials was introduced to minimize inconvenience. In the past, different materials used for drainpipe construction were purchased per construction site and placed on the road, causing inconvenience to pedestrians. Currently, however, the Material Management Office makes integrated purchase and management to improve the drawbacks.

Policy Outcome & Evaluation

Thanks to efforts to repair and replace old water pipes, we can now ensure the stable supply of clean and safe tap water. Not only that -- we were able to increase the revenue water ratio by cutting leak. In addition, we introduced GIS in the maintenance and management system of the water pipe network. Since GIS creates a systematic database and turns into figures and maps the design and properties information of water pipes, supporting components, valves, fire hydrant, and water meter as well as their attributes and current data, we can efficiently manage all data on the water pipe network in Seoul.
Meanwhile, we strengthened the capacity of our civil servants who have accumulated expertise and experience in the process, and they have become an important asset not just for Seoul but also the entire country.
Tangible Outcomes of the Old Water Pipe Maintenance Project
 • Reduced Leak (DOWN by 82.5%): In 1989, before replacing old pipes, 59,438 cases of leak were observed. In 2013, after replacing old pipes, the number went down to 10,421.
 • Increase in revenue water ratio (UP by 171%): In 1989, before replacing old pipes, Seoul’s revenue water ratio was 55.2 %; it surged to 94.4% in 2013, however.

Applicability of the Policies

Seoul’s experiences in establishing the “Basic Plan for Waterworks Improvement,” introducing the operation of GIS & integrated control station for water supply, and increasing the revenue water ratio are some of the good practices that can be benchmarked by other municipalities in Korea as well as Southeast Asian countries.
Applicable Areas
 • Establishing a water supply system in line with the old water pipe maintenance and stable water supply infrastructure
 • Presenting the mid- to long-term path of water system maintenance
 • Building small- and medium-sized blocs in line with the old water pipe maintenance
 • Measuring the nighttime minimum flow rate, enhancing the revenue water ratio, and performing post construction impact analysis on old pipe maintenance


Seoul is about to complete the old water pipe replacement project. Soon, however, some water corrosion-resistant pipes that replaced the old pipes will see their life span expire. Does Seoul have plans to replace those as well?
 • Replacing old pipes with new ones began in 1984. By the end of 2013, 2.8 trillion won was spent on the replacement of 13,192km out of 13,668km old pipes with new ones, for a maintenance rate of 96.5 %. In 2014, we expanded our scope even further to include coal tar enamel-coated steel pipes, and a total of 13,728km will be replaced by 2018.
 • From 2014, we will begin evaluating the deterioration of pipes over 30 years old or ductile cast iron pipes, steel pipes, and stainless pipes that will soon exceed their life span. We will use the assessment factors listed in the guidelines set forth by the Ministry of Environment titled “Water Pipe Network Optimum Control System and Standard Maintenance Guidelines.” Through the evaluation project, we will ensure that our water pipe network is maintained at its highest quality.