About İSKİ


Statistics on Istanbul

Population Served : 15 million 462 thousand 452
Total Area of Service : 5 thousand 461 km2
Number of Subscribers :
6 million 677 thousand 201
Length of Water Network : 19 thousand 804 km
Length of Transmission Lines : 3 thousand 052 km
Yield of Water Resources : 1 billion 653 million m³/year
Average daily water supply : 3 million 103 thousand 614 m³/day
Number of Potable Water Treatment Plants : 21
Capacity of Potable Water Treatment Plants : 4 million 352 thousand 220 m³/day
Number of Water Storage Tanks : 153
Volume of Water Storage Tanks : 1 million 787 thousand 080 m³
Total length of sewers : 16 thousand 746 km
Length of Collector Lines : 1197 km
Length of Tunnels : 201 km
Number of Wastewater Treatment Plants : 90
Capacity of Wastewater Treatment Plants : 5 million 813 thousand 410 m³/day

Administrative Structure

Founded in 1981 with the launch of İSKİ Law No. 2560, İSKİ is a public utility of Istanbul Metropolitan Municipality with an independent budget. The managerial board of the administration where the Mayor of Istanbul is the Board Chairman is the Metropolitan Municipality Council. The General Director of İSKİ is elected upon the proposal of the Metropolitan Municipality Mayor and approved by the Minister of Interior Affairs. The General Director of İSKİ also acts as the Vice Chair of the Management Board which also includes 4 members including a senior Deputy General Director. Two inspectors elected by the İSKİ General Board (Municipal Assembly) conduct inspection services.

The administration includes 5 Deputy General Director Offices, Department of Inspection Committee, Legal Advisor’s Office, Internal Auditing Unit, 20 Departments and 104 Directorates. A total of 9,905 staff includes 7,100 workers and 2,805 officers with a majority of technical background.

A great majority of the income of İSKİ is from the water sales. Most of the investments are conducted through this income from water sales.

To receive İSKİ’s services, water and wastewater subscription is required through a contract with İSKİ. Water consumption is identified and measured via mechanical or smart meters. Contracts are classified according to the consumer groups of households, businesses, public institutions, industrial locations, village settlements and offices as well as municipal buildings. İSKİ currently has about 6.6 million subscribers.

Water Management

99% of water resources in Istanbul are surface water resources. The annual yield of drinking water resources is 1 billion 653 million m3. 60% of water resources are on the Asian side with 40% of population, while 40% of the water is on the European side with 60% of the population.

Water collected in the resources is delivered to drinking water treatment plants via transmission lines reaching a total length of 3,052 km.

The rough geography and distance of water resources to the city in Istanbul brings about a large energy requirement. In every stage between the water resource and house taps, pumping systems were installed to enable pressure supply. The pumps of various capacities in 105 pumping stations all around Istanbul provide water to all corners of the city. The annual energy consumption is 1.6 billion kWh.

Raw water in the drinking water resources reach to the water treatment plants via transmission lines for the required treatment processes. There are 21 potable water treatment plants in Istanbul. Ozone systems are adopted in these plants that have a total capacity of 4.35 million m3/day to enable provision of water with potable standards.

Upon treatment, the water is supplied to the people in Istanbul via the transmission lines, drinking water network in the distribution system. The drinking water network is made of ductile iron pipes. This pipe type is selected due to its resistant, leak-proof and long-lasting aspects.

Laboratory services

The quality of water treated at potable water treatment plants is analyzed at the laboratories in the same plants of İSKİ. Starting from the entry of raw water into the plant through the whole treatment process, the analyses conducted provide continuous monitoring of the quality of water supplied to the potable water distribution system. Over 163 parameters, including chemical, bacteriological and aesthetic ones, are monitored in the process. Furthermore, an average of 80-100 samples are taken from points where the water meets the residents of Istanbul in regions fed by each distribution system and analyzed in the labs. The results of these analyses are accessible monthly over the web page of İSKİ.

The whole potable water system of Istanbul is managed via the central command system called SCADA. All data on occupancy rate of water resources, rainfall, pressure values in potable water lines, water value in storage tanks are transferred instantly to the center, which can directly address to the system.

Wastewater Management

The used water that becomes wastewater is collected via a wastewater network of 16,482 km in length. Concrete pipes are the main material of the wastewater lines. Wastewater is transferred to collector and tunnels through the network. The collector lines are made up of concrete pipes resisting to corrosion and with high durability. In locations where open dig is not possible due to traffic density, ground conditions, regional geographical aspects, wastewater lines are dug via tunnel methods. Almost all of the coasts in Istanbul have been laid with wastewater collectors and tunnels with a diameter of up to 3 m. Robot technologies are used for the repair and maintenance works of the lines. Any blockage in the wastewater lines can be identified and cleaned by the camera robots and the breakdowns are fixed with no-dig coating, enabling longer pipe use.

Wastewater collected through collectors and tunnels is delivered to wastewater treatment plants. There are 89 wastewater treatment plants with different capacities planned in line with the requirements of the basin it serves within Istanbul. Considering the dynamic structure of the Bosphorus, the Bosphorus coasts were installed with primarily pre-treatment plants while biological and advance biological treatment processes were selected for locations along Marmara Sea.

Part of the outlet water from advance biological wastewater treatment plants is used for the irrigation of recreational areas and industrial water upon the final disinfection process. A significant amount of the energy required for the process of treatment plants is obtained via wastewater as well.