The potable water supply network is divided into two parts:

• Main pipelines are pipelines with large diameters of 250 mm or more. The main pipelines are used to transmit the potable water from the intake towers to the distribution pipelines. Currently, PPWSA’s largest main pipelines have a diameter of 1,600 mm. Because of the water pressure in the pipelines, it is mandatory that the main pipelines are constructed of Ductile Iron.

• Water distribution pipelines consist of pipelines with diameters of from 50mm – 200mm. Water distribution pipelines are used to distribute treated water from the transmission mains to customers. PPWSA currently uses HDPE pipes for the distribution network because they are relatively inexpensive and offer reasonable quality. All of the pipes used in the water distribution network are constructed if HDPE except for the pipelines in Khan 7 Makara and some areas of Khan Tuol Kork which use Ductile Iron, and which were financed by a grant from the Japanese Government. Commencing in 1993, PPWSA’s main and water distribution pipelines have been continuously replaced, upgraded and extended. Cast Iron pipes have been replaced with Ductile Iron pipes, and additional distribution pipelines have been installed in many of PPWSA’s service areas, to extend coverage in those areas. This differentiates PPWSA, whose pipelines have been almost entirely replaced or installed in the years from 1993, from many of other water authorities in the region, who have old legacy pipelines. The process of the restoration of PPWSA’s pipelines was as follows:

• In 1993 the French Government provided grant aid to replace the 8km at size from 80mm to 200 mm long water distribution pipelines in Sangkat Sras Chak, Khan Daun Penh. The primary purpose of this project was to provide training to the employees of PPWSA at that time in the installation of water distribution pipelines.

• From 1994 to 1996, PPWSA continued to replace old pipelines with the length of 68 km and extend the service area in Khan Daun Penh with financing from development partners, including the WB and ADB. The financing from both banks was used to purchase pipeline and connection materials. PPWSA contributed funds to lay the pipelines.

• In 1997 – 1999, the grant of Japanese aid through JICA enabled the replacement of old pipelines and extensions having a length of 68km to the service areas in the Khan Daun Penh, Khan 7 Makara and a part of Khan Tuol Kok. This grant included the provision of pipelines and installation. At the same time, PPWSA installed new pipelines having a length of 99 km in Khan Chamkar Mon which were financed by a loan from the ADB.

• From 1998 to 2001, the WB and ADB continued to provide financing for the replacement of old pipelines and extensions at the length of 221 km to the service area in Khan Chamkar Mon and Khan Tuol Kok.. Besides, to ensure that the pipeline had adequate capacity, the existing dilapidated main pipeline which had a diameter of 700 mm was replaced with a pipeline ranging in diameter from 900 mm to 1,600 mm. The replacement of the main pipeline was done with financing obtained from the ADB.

• After replacing the old pipelines and extending the distribution network in the existing service areas, commencing in 2002 new pipelines were installed to expand into new service areas. This expansion is continuing with financing from the WB, ADB and AFD. The graph below shows the length of pipeline installed each year since 1993 and the cumulative length of the pipelines:

In addition to the main and water distribution pipelines, the transmission and distribution system contains four water reserve basins for meeting water demand both in terms of quantity and water pressure at the boundaries of the service area. These basins can store 1.500 m3 of treated water, and are built to a height of 30 meters from the ground in order to be able to supply additional water pressure when there is high demand. Grant aid from the AFD was used to finance the construction of two water reserve basins: Chaom Chao Water Reserve Basin and Pochentong Water Reserve Basin. The WB also provided financing for the construction of two water reserve basins: Chraing Chamres Water Reserve Basin and Takhmao Water Reserve Basin.