The Polydendri facilities are located between the national road connecting Athens to Lamia and the Marathon Reservoir. The plant has an altitude of approximately +237 m. The facilities occupy an area of 10,75 hectares and have been in operation since 1986.

The water it treats is first pumped from the Yliki-Marathon aqueduct to the plant via the Kiourka pumping station. This WTP can treat raw water from all the alternative water sources (Mornos Reservoir, Yliki Lake and the Boreholes of Mavrosouvala, Viliza and Yliki). The treated (potable) water is distributed to the following areas: the eastern coast of Attica (from Marathon to Lavrio), the southern coast of Attica (from Lavrio to Vari), as well as the northern suburbs of Athens (Ag. Stefanos, Varibobi, Thrakomakedones and portions of Kifissia).

The plant’s total daily water treatment capacity is 200.000 m3, reaching 300.000 m3 during peak periods.